Assumptions HubMethodology v1.2.0Verified August 2026 Data

Coast FIRE Calculator Assumptions & Methodology

Coast FIRE calculations depend on a small set of assumptions: investment growth, inflation, investment costs, retirement spending, withdrawal rate, and time.

This page explains the assumptions used when our Coast FIRE Calculator first loads, shows exactly how they affect the calculation, and compares them with verified economic and market data.

Nominal Return
7.0%
Calculator AssumptionEditable
Inflation
3.0%
Calculator AssumptionEditable
Investment Fees
0.10%
Calculator AssumptionEditable
Withdrawal Rate
4.0%
Calculator AssumptionEditable
Σ
Net Real ReturnCalculated from current defaults
3.79%/ year
DEFAULT ≠ RECOMMENDATION

Calculator defaults are starting values for a mathematical model. They are not forecasts, guarantees, or recommendations.

All four assumptions are editable. Changing one or more of them changes the modeled Coast FIRE result. Default does not mean recommended.

📑 Table of Contents▼

Live Calculator Defaults

AssumptionCurrent DefaultWhat It Means
Nominal investment return7.0%Annual investment-growth assumption before inflation and modeled fees
Inflation3.0%Annual price-growth assumption used to convert nominal growth into real purchasing-power growth
Investment fees0.10%Annual investment-cost assumption deducted by the model
Withdrawal rate4.0%Assumption used to convert annual retirement spending into a modeled retirement portfolio target
Net real return3.79%Result produced by the calculator's current return, inflation, and fee assumptions

All four assumptions are editable.

Changing one or more of them changes the modeled Coast FIRE result.

Default does not mean recommended.

Not Every Percentage Means the Same Thing

Financial percentages often appear next to one another even though they describe very different things.

Our site separates them into five categories.

01

Observed Data

Observed Data

A measurement of something that has already happened.

Example: 3.4% CPI inflation for the 12 months ending July 2026.

That is an observed historical statistic. It is not a 30-year inflation forecast.

02

Historical Result

Historical Result

A return or other result measured over a completed historical period.

Examples include the past performance of the S&P 500 or another investment index.

Historical returns can provide context, but they do not determine future investment returns.

03

Market-Implied Measure

Market-Implied

A value inferred from prices in financial markets.

One example is the 10-Year Breakeven Inflation Rate, which is derived from the difference between nominal Treasury yields and inflation-protected Treasury yields.

This is a market-implied measure rather than a guaranteed forecast.

04

Policy Goal or Projection

Policy Goal

A target or projection published by a government or policy institution.

For example, the Federal Reserve states a 2% longer-run inflation goal measured using the PCE price index.

A policy goal is different from both current inflation and a Coast FIRE calculator assumption.

05

Calculator Assumption

Calculator Assumption

A value entered into a mathematical model.

• 7% nominal return
• 3% inflation
• 0.10% investment fees
• 4% withdrawal rate

These values tell the calculator what scenario to calculate. They do not tell us what will happen in the future.

How the Coast FIRE Math Connects

The calculator combines three main calculations.

Stage 1

Retirement Portfolio Target

Spending ÷ Withdrawal-Rate Assumption

$50,000 ÷ 4% = $1,250,000
Stage 2

Fee- & Inflation-Adjusted Growth

((1 + Nominal − Fees) ÷ (1 + Inflation)) − 1

Real Return ≈ 3.79%
Stage 3

Coast FIRE Present Value

Target ÷ (1 + Real Return)^Years

Coast FIRE Number = $340,403

Stage 1: Calculate the Retirement Portfolio Target

The calculator starts with modeled annual retirement spending.

The basic relationship is:

Retirement Portfolio Target = Annual Retirement Spending ÷ Withdrawal-Rate Assumption

For example:

$50,000 ÷ 4% = $1,250,000
So $50,000 of annual modeled retirement spending with a 4% withdrawal-rate assumption produces a:$1.25 million modeled retirement target

The 4% figure is an example calculator input, not a statement that 4% is appropriate for every retirement.

Stage 2: Calculate the Fee- and Inflation-Adjusted Return

Our calculator currently uses:

Real Return = ((1 + Nominal Return − Fees) ÷ (1 + Inflation)) − 1

Using the current defaults:

  • nominal return = 7%
  • investment fees = 0.10%
  • inflation = 3%
the calculator produces a real return of approximately:3.79%

This is the calculator's fee-adjusted, inflation-adjusted growth rate.

It should not be interpreted as a prediction of future real investment returns.

Stage 3: Calculate the Coast FIRE Number

The calculator then works backward from the future retirement target.

Coast FIRE Number = Retirement Portfolio Target ÷ (1 + Real Return)^Years Until Retirement

This is a present-value calculation.

It asks:

How much would need to be invested today for the model to reach the selected future retirement target under the assumptions entered?

Why Assumptions Matter

The Coast FIRE calculation contains compound growth.

That means changing return, inflation, investment fees, or the number of years until retirement can change the modeled starting amount substantially.

Retirement spending and the withdrawal-rate assumption also matter because they determine the future portfolio target.

The important point is not that one assumption is "better."

The important point is that different assumptions produce different mathematical results.

1. Investment Return Assumption

Current Default: 7.0%

Current Calculator Default: 7.0% Nominal

The nominal investment return is the annual growth rate entered before the calculator adjusts for inflation and modeled investment fees.

Our current starting value is:7.0% nominal

This is an editable calculator assumption.

It is not a forecast of future portfolio performance.

WHAT THIS NUMBER IS
TYPECalculator Assumption
CURRENT DEFAULT7.0%
USER EDITABLEYes
FORECAST?No

Historical Returns and Future Returns Are Different

Historical stock-market returns can provide useful context, but several choices affect any historical return number:

  • which index is measured;
  • which start and end dates are used;
  • whether dividends are included;
  • whether the number is nominal or inflation-adjusted;
  • whether investment costs are deducted;
  • and whether the return is an arithmetic average or compound annualized return.

For this reason, we do not treat one historical market average as the automatically correct Coast FIRE return assumption.

The S&P 500, maintained by S&P Dow Jones Indices, is one commonly referenced U.S. large-cap equity index.

Its historical performance changes depending on the period measured.

Past index performance does not establish what a future portfolio will earn.

Average Return Is Not Always Compound Return

Imagine an investment starting at $100.

Year 1

Return:+50%
Portfolio:$100 → $150

Year 2

Return:−50%
Portfolio:$150 → $75

The simple arithmetic average of +50% and −50% is:

0%

But the portfolio did not return to $100. It ended at:

$75

This is why simply averaging yearly returns is not the same as measuring compounded investment growth.

FINRA educational material distinguishes annualized performance from simple averages when evaluating returns over multiple periods.

How Changing the Return Assumption Changes Coast FIRE

The following example keeps everything else constant:

  • annual retirement spending: $50,000
  • withdrawal-rate assumption: 4%
  • retirement target: $1,250,000
  • inflation: 3%
  • investment fees: 0.10%
  • years until retirement: 35
Return ScenarioReal ReturnModeled Coast FIRE Number
5.0% 1.84%$659,281
6.0% 2.82%$472,993
7.0% Current Default3.79%$340,403
8.0% 4.76%$245,732
9.0% 5.73%$177,925

These are mathematical scenarios.

They are not forecasts of investment returns.

A higher assumed return gives the model more compound growth and therefore produces a lower present-value Coast target.

A lower assumed return produces a higher present-value target.

Deeper AnalysisWant to explore historical asset returns and CAGR?
How return assumptions change Coast FIRE →

2. Inflation Assumption

Current Default: 3.0%

Current Calculator Default: 3.0%

Inflation describes changes in prices over time.

Our calculator uses inflation when converting nominal investment growth into a real, purchasing-power-adjusted return.

The current calculator starting value is:3.0% per year

This is a long-term model input.

It is not the current inflation rate and it is not an inflation forecast.

WHAT THIS NUMBER IS
TYPECalculator Assumption
CURRENT DEFAULT3.0%
USER EDITABLEYes
FORECAST?No

Inflation Is Not One Number

Several useful inflation-related figures are available today, but they answer different questions.

CURRENT CPI
3.4%
Observed Data
July 2026 (Core: 2.5%)
U.S. Bureau of Labor Statistics
CURRENT PCE
3.7%
Observed Data
June 2026 (Core: 3.3%)
U.S. Bureau of Economic Analysis
10-YEAR BREAKEVEN
2.31%
Market-Implied Measure
August 28, 2026
FRED St. Louis Fed
FEDERAL RESERVE GOAL
2.0% PCE
Policy Goal
Longer-run target
Federal Reserve FOMC
CALCULATOR ASSUMPTION
3.0%
Calculator Assumption
User editable scenario baseline

Current CPI Inflation

The U.S. Bureau of Labor Statistics reported that the Consumer Price Index for All Urban Consumers increased 3.4% over the 12 months ending July 2026.

The CPI excluding food and energy increased: 2.5%

Type: Observed Data • Source: U.S. Bureau of Labor Statistics

This describes price changes over the previous 12 months. It does not describe what inflation will average over the next 20, 30, or 40 years.

Current PCE Inflation

The U.S. Bureau of Economic Analysis reported that the PCE price index increased 3.7% from June 2025 to June 2026.

PCE excluding food and energy increased: 3.3%

Type: Observed Data • Source: U.S. Bureau of Economic Analysis

PCE and CPI are related measures, but they are constructed differently.

10-Year Breakeven Inflation

The Federal Reserve Bank of St. Louis FRED series reported 2.31% on August 28, 2026 for the 10-Year Breakeven Inflation Rate.

Type: Market-Implied Measure

The breakeven rate is derived from nominal Treasury securities and Treasury Inflation-Protected Securities. It reflects a market-implied inflation measure over approximately the next 10 years. It is not guaranteed future inflation.

Federal Reserve Longer-Run Inflation Goal

The Federal Reserve states that its longer-run inflation goal is 2% measured using the: Personal Consumption Expenditures Price Index.

Type: Policy Goal

This is not the same as current CPI. It is also not the same thing as the calculator's 3% inflation assumption.

Calculator Inflation Assumption

Our calculator currently starts at:3.0%
Type: Calculator Assumption

These figures should not be blended together as though they mean the same thing.

Inflation FigureCurrent ValueType
CPI-U, 12 months ending July 20263.4%Observed data
Core CPI2.5%Observed data
PCE, 12 months ending June 20263.7%Observed data
Core PCE3.3%Observed data
10-Year Breakeven, Aug. 28, 20262.31%Market-implied
Federal Reserve longer-run goal2.0% PCEPolicy goal
Coast FIRE calculator3.0%Calculator assumption
Observed inflation, market expectations, policy goals, and calculator assumptions answer different questions.

CPI and PCE Are Different

CPI
Publisher: U.S. Bureau of Labor Statistics
Purpose: consumer-price measure
PCE
Publisher: U.S. Bureau of Economic Analysis
Federal Reserve goal: expressed using PCE inflation

CPI and PCE both measure consumer-price changes, but they are not identical.

The Bureau of Labor Statistics publishes CPI.

The Bureau of Economic Analysis publishes the PCE price index.

The Federal Reserve defines its 2% longer-run inflation goal using PCE inflation.

That is why a statement such as:

"The Fed target is 2%"

should not be interpreted as:

"CPI will be 2%."

They are different concepts.

How Changing Inflation Changes the Coast FIRE Result

This example keeps:

  • nominal return: 7%
  • fees: 0.10%
  • retirement spending: $50,000
  • withdrawal-rate assumption: 4%
  • years until retirement: 35
Inflation ScenarioNet Real ReturnModeled Coast FIRE Number
2.0% 4.80%$241,934
2.5% 4.29%$287,095
3.0% Current Default3.79%$340,403
3.5% 3.29%$403,276
4.0% 2.79%$477,372

These are mathematical scenarios, not inflation forecasts.

With all other inputs unchanged, a higher inflation assumption lowers the model's real growth rate and increases the Coast FIRE amount required today.

Deeper AnalysisUnderstand the math between constant dollars and nominal returns.
Read Real Return vs Nominal Return →

3. Investment Fees

Current Default: 0.10%

Current Calculator Default: 0.10%

Investment fees are costs that reduce the return remaining in the model to compound.

Our calculator currently starts with:0.10% per year

The calculator deducts the selected fee assumption from nominal growth before applying its inflation adjustment.

This is a simplified annual modeling input.

Actual investment costs depend on the investments, account, plan, and services involved.

WHAT THIS NUMBER IS
TYPECalculator Assumption
CURRENT DEFAULT0.10%
USER EDITABLEYes
FORECAST?No

What Current Fund-Fee Data Shows

The Investment Company Institute reported the following asset-weighted average expense ratios for 2025:

INDEX BOND ETF0.09%
INDEX EQUITY ETF0.14%
BOND MUTUAL FUND0.36%
EQUITY MUTUAL FUND0.40%

2025 asset-weighted averages reported by ICI. These figures describe categories in ICI's dataset. They do not determine the cost of an individual portfolio. They also do not mean the calculator's 0.10% default applies to every investor.

What Fees Can Include

Investment costs can take different forms.

Depending on the account or investment arrangement, costs may include:

  • fund expense ratios;
  • investment-management costs;
  • plan administration fees;
  • advisory fees;
  • account or service fees;
  • transaction-related costs.

The U.S. Department of Labor's Employee Benefits Security Administration separately discusses plan administration, investment, and individual service fees in retirement plans.

Our calculator uses one annual fee percentage as a simplified model input.

SEC Example: Why Fee Differences Compound

Investor.gov provides a hypothetical example starting with $100,000 with 4% annual growth over 20 years:

0.25% fee≈ $208,000
0.50% fee≈ $198,000
1.00% fee≈ $179,000
Annual FeeApproximate Ending Value
0.25%$208,000
0.50%$198,000
1.00%$179,000

This SEC example demonstrates the mathematical effect of ongoing fees over time.

It does not identify an appropriate Coast FIRE fee assumption.

How Changing Fees Changes the Coast FIRE Result

This example keeps:

  • nominal return: 7%
  • inflation: 3%
  • retirement spending: $50,000
  • withdrawal-rate assumption: 4%
  • years until retirement: 35
Annual Fee ScenarioNet Real ReturnModeled Coast FIRE Number
0.03% 3.85%$332,693
0.10% Current Default3.79%$340,403
0.50% 3.40%$388,129
1.00% 2.91%$457,623
1.50% 2.43%$539,979

These are model scenarios.

They do not describe the fees of any particular investment account.

Want to isolate investment costs?Calculate fee drag compounding on your portfolio.
Investment Fee Impact Calculator →

4. Withdrawal-Rate Assumption

Current Default: 4.0%

Current Calculator Default: 4.0%

The withdrawal-rate assumption converts modeled annual retirement spending into a future retirement portfolio target.

The relationship is:

Retirement Portfolio Target = Annual Retirement Spending ÷ Withdrawal Rate
WHAT THIS NUMBER IS
TYPECalculator Assumption
CURRENT DEFAULT4.0%
USER EDITABLEYes
FORECAST?No

For $50,000 of annual retirement spending:

Withdrawal-Rate ScenarioSpending MultipleModeled Retirement Target
3.0% 33.3×$1,666,667
3.25% 30.8×$1,538,462
3.5% 28.6×$1,428,571
4.0% Current Default25.0×$1,250,000
4.5% 22.2×$1,111,111

A lower withdrawal-rate assumption creates a larger modeled retirement target.

A higher withdrawal-rate assumption creates a smaller modeled retirement target.

That is a mathematical relationship.

It does not establish which percentage applies to a particular retirement.

Where the 4% Discussion Comes From

The commonly discussed 4% withdrawal concept has roots in historical retirement research.

CARD 1 • RESEARCH STUDY

William P. Bengen

"Determining Withdrawal Rates Using Historical Data"

Journal of Financial Planning
1994
CARD 2 • TRINITY STUDY

Philip L. Cooley, Carl M. Hubbard, Daniel T. Walz

"Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable"

Trinity University Study
1998

In 1994, William P. Bengen published "Determining Withdrawal Rates Using Historical Data" in the Journal of Financial Planning. The study examined retirement withdrawals using historical U.S. investment returns and inflation data.

In 1998, Philip L. Cooley, Carl M. Hubbard, and Daniel T. Walz published "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable". The research examined different:

  • withdrawal rates;
  • portfolio allocations;
  • retirement periods;
  • and historical market sequences.

Those studies describe results produced by their specific historical datasets and assumptions.

They do not guarantee future retirement outcomes.

Our calculator's 4% value is therefore labeled an editable withdrawal-rate assumption, not a guaranteed withdrawal rule.

How Withdrawal Rate Changes the Coast FIRE Number

Keeping these values constant:

  • annual retirement spending: $50,000
  • nominal return: 7%
  • inflation: 3%
  • fees: 0.10%
  • years until retirement: 35
Withdrawal RateRetirement TargetModeled Coast FIRE Number
3.0% 33.3×$1,666,667
3.25% 30.8×$1,538,462
3.5% 28.6×$1,428,571
4.0% Current Default25.0×$1,250,000
4.5% 22.2×$1,111,111

These percentages are scenario inputs.

They are not recommendations.

Deeper AnalysisExplore withdrawal-rate research and how different assumptions change the modeled target.
Understand withdrawal-rate assumptions →

Change One Assumption

The easiest way to understand assumptions is to keep everything else unchanged.

Example scenario: The ages, spending, portfolio balance, savings amount, and percentages shown below are demonstration inputs used to explain the calculator. They are not suggested or typical values.

Example baseline:

Current age: 30
Retirement age: 65
Time: 35 years
Retirement spending: $50,000/year
Nominal return: 7%
Inflation: 3%
Investment fees: 0.10%
Withdrawal rate: 4%

Baseline result:

Retirement target: $1,250,000
Net real return: 3.79%
Modeled Coast FIRE number: approximately $340,403

Changing only one input lets you see which part of the calculation moved.

Change return

Changes the modeled real growth rate.

Change inflation

Changes the modeled real growth rate.

Change fees

Changes the modeled real growth rate.

Change withdrawal rate

Changes the modeled retirement portfolio target.

Interactive Sensitivity ToolProduction Engine v1.2.0

Change One Assumption

Isolate any single variable below to see how it shifts your required starting capital and growth rate against baseline defaults.

HorizonAge 30→65 (35y)
Annual Spending$50,000/yr
Current Portfolio$50,000
Monthly Savings$500.00/mo

Scenario context only: Current portfolio and monthly savings are shown for context in this example. They do not change the Coast FIRE target calculated in this assumption comparison.

Expected Nominal ReturnControls gross growth rate before fee drag and inflation.
7.00%
3.0% scenario7.0% current default12.0% scenario
BASELINEDefaults
Coast FIRE Number$340,403
Retirement Target: $1,250,000
Real Return: 3.79%
SELECTED SCENARIOLive
Coast FIRE Number$340,403
Retirement Target: $1,250,000
Real Return: 3.79%
DIFFERENCEDelta
Starting Capital+$0.00
Target: $0
Real Return: +0.00%
Want multi-variable scenario testing?

This page isolates single variables. The Assumption Lab allows full multi-variable stress testing.

Open Full Assumption Lab →

How All Four Assumptions Work Together

The calculation can be viewed as two paths.

RETIREMENT-TARGET PATH
Annual retirement spending
↓
Withdrawal-rate assumption
↓
Modeled retirement portfolio target
GROWTH PATH
Nominal investment return
↓
Investment fee adjustment
↓
Inflation adjustment
↓
Modeled real growth rate

The two paths then combine with time:

Retirement target+real growth+years to retirement
↓
modeled Coast FIRE number today

Exact Calculator Formula

The current production calculation engine implements the following exact functions:

1. Retirement Portfolio Targetfire-target.ts
target = adjustedSpending / withdrawalRate;
2. Fee-Adjusted Real Return (Calculator Formula)real-return.ts
export function calculateRealReturn(
  nominalReturn: number,
  inflationRate: number,
  fees: number
): number {
  const netNominal = 1 + nominalReturn - fees;
  const inflationFactor = 1 + inflationRate;

  if (inflationFactor <= 0) {
    throw new RangeError('Inflation factor must be positive');
  }

  return netNominal / inflationFactor - 1;
}
3. Coast FIRE Present Valuecoast-fire.ts
coastFireNumber = target / Math.pow(1 + realReturn, yearsToRetirement);
Technical ImplementationNeed the full mathematical specification and test suites?
See the full mathematical methodology →

Verified Sources & Methodology Registries

The external figures and research references used on this page are linked to government agencies, regulators, Federal Reserve data, index providers, industry research organizations, and original research sources.

Full source registry →
U.S. Bureau of Labor StatisticsGov Tier 1 ↗

CPI-U July 2026: 3.4%

Government Statistical Agency

Bureau of Economic AnalysisGov Tier 1 ↗

PCE Price Index June 2026: 3.7%

Government Statistical Agency

Federal Reserve Bank of St. LouisFed Tier 1 ↗

10-Year Breakeven Aug 28, 2026: 2.31%

Federal Reserve Market Data (T10YIE)

Federal ReservePolicy Goal ↗

2% PCE Longer-Run Goal

Policy Institution

S&P Dow Jones IndicesIndex Provider ↗

S&P 500 Historical Context

Historical index performance is used as market context only. It does not determine the calculator's future return assumption.

Investment Company InstituteIndustry ↗

2025 Asset-Weighted Expense Ratios

Industry Research

SEC Investor.govRegulator ↗

$100k 20-Yr Fee Impact Study

U.S. Securities & Exchange Commission

FINRAInvestor Ed ↗

Annualized Return Concepts

Financial Industry Regulatory Authority

U.S. Department of Labor (EBSA)Gov Tier 1 ↗

Retirement-Plan Fee Categories

Employee Benefits Security Administration

William P. BengenResearch ↗

Withdrawal-Rate Study (1994)

Journal of Financial Planning • FPA

Philip L. Cooley, Carl M. Hubbard, Daniel T. WalzHistorical Research ↗

Trinity Study (1998)

Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable • AAII

Frequently Asked Questions

Common questions about calculator defaults, inflation math, and long-term planning assumptions.

How were the default baseline assumptions (7% return, 3% inflation, 0.10% fees, 4% SWR) selected?▼
The default baseline values reflect widely cited long-term empirical benchmarks: secular US broad-market equity growth (historical S&P 500 ~7–10% nominal), multi-decade average US CPI inflation (~2.5–3.0%), asset-weighted passive index fund expense ratios (ICI data), and the foundational Trinity Study withdrawal framework (Bengen 1994, Cooley et al. 1998). They serve as standard educational reference points, not prescriptive personal recommendations.
Why does the calculator use real (inflation-adjusted) returns instead of nominal compounding?▼
Using real returns allows all figures—including your desired retirement spending and resulting Coast FIRE target—to be expressed in constant, today's purchasing power. This prevents the distortion of trying to estimate what a loaf of bread, rent, or health insurance will cost 30 years from now.
How are investment fees subtracted in the calculation engine?▼
In our production engine, investment fees are deducted directly from expected nominal returns in the numerator of the Fisher equation before adjusting for inflation: Real Return = ((1 + Nominal Return - Fees) ÷ (1 + Inflation Rate)) - 1. This ensures that fees drag down nominal compound growth before purchasing-power discounting is applied.
How do short-term inflation or market changes relate to long-term calculator assumptions?▼
Coast FIRE horizons often span multiple decades, but actual returns can vary substantially within them. The Assumption Lab can compare a baseline with lower-return and adverse scenarios without treating any calculator default as a recommendation.
Why do different Coast FIRE calculators give completely different targets?▼
Discrepancies usually stem from technical differences: whether the model uses nominal vs. real math, the chosen safe withdrawal rate (e.g., 3.25% vs 4.0%), whether investment fee drag is included, whether monthly compounding vs annual compounding is applied, and how pensions or Social Security offsets are discounted.
Do calculator defaults represent guaranteed or "safe" financial outcomes?▼
No. No assumption set can guarantee future financial independence. All market investments carry sequence of returns risk, market volatility, and macroeconomic uncertainty. Calculator outputs are mathematical models intended for educational and scenario-planning purposes only.
How We Maintain These AssumptionsProduction Engine v1.2.0 • Methodology v1.2.0
LAST REVIEWEDSeptember 7, 2026
DATA BENCHMARKSJuly / August 2026
EDITORIAL REVIEWCoast FIRE Calculator
TEST SUITE VALIDATIONAutomated Calculation Checks
Methodology•Data Sources•Calculator Changelog•Editorial Policy

Selected Next Steps

Ready to model your own numbers or explore specific life scenarios?

Core Calculator

Main Coast FIRE Calculator

Calculate your Coast FIRE date and portfolio target with live inputs.

Scenario Testing

Coast FIRE Assumption Lab

Stress-test custom multi-variable return, inflation, and fee scenarios.

Advanced Modeling

Advanced Coast FIRE Calculator

Integrate pension streams, Social Security, and bridge income.

Step-by-Step Guide

How to Calculate Coast FIRE

Worked manual calculation examples and formula walk-throughs.

Mathematical Guide

Coast FIRE Formula Explained

Comprehensive breakdown of compound growth and discounting math.

Documentation

Full Calculation Methodology

Detailed formulas, engine architecture, and calculation documentation.