Turn this estimate into an ongoing plan
Coast FIRE is not a one-time number. Use BeCoin to follow markets, review forecasts and keep the assumptions behind your investing plan visible as conditions change.
Free retirement planning tool
Find the point where your money can coast.
Calculate how much you need invested today for compound growth to carry you to retirement. See your Coast FIRE number, likely coast age, future gap and three return scenarios—in today’s dollars.
Your Coast FIRE plan
Use long-term estimates, not a recent year’s performance. Results update as you type.
Your age today.
When withdrawals are expected to begin.
Desired yearly spending in today’s dollars.
Retirement investments—not emergency cash.
Used to estimate your future coast age.
Nominal return before inflation and fees.
Used to keep results in today’s dollars.
Fund and advisory fees, if applicable.
A planning assumption, not a guarantee.
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Coast FIRE calculator guide
The calculator separates three questions: what retirement may cost, how much needs to be invested now, and whether continued contributions could move your coast date earlier.
Compare return scenarios
Small changes in long-term returns create large changes over decades. These cases hold every input constant and vary the nominal return by two percentage points.
Your path to retirement
The blue line projects your portfolio with the entered monthly contribution. The green line is the minimum balance needed at each age to coast to the same retirement target.
Projected portfolioCoast threshold
| Age | Projected portfolio | Coast threshold | Status |
|---|
How to use the Coast FIRE calculator
1. Define retirement
Choose a retirement age and annual spending level in today’s dollars. Spending divided by the withdrawal rate creates the retirement target.
2. Add your investments
Enter assets already invested for retirement and the monthly contribution you expect to continue until reaching Coast FIRE.
3. Stress-test assumptions
Review the conservative, base and optimistic cases. A robust plan should not depend on one precise return forecast.
How the Coast FIRE formula works
First, the calculator estimates the amount needed when retirement begins:
Retirement target = annual spending ÷ withdrawal rate
It then discounts that target back to today using the years remaining and an estimated real return:
Coast number today = retirement target ÷ (1 + real return)years
Real return
The tool calculates (1 + return after fees) ÷ (1 + inflation) − 1. This is more precise than simply subtracting inflation, and lets every displayed dollar keep today’s purchasing power.
Future contributions
Your projected portfolio includes monthly deposits compounded at the monthly real rate. Coast age is the first age when that projection meets the coast threshold for the time remaining.
Interpretation: if invested assets equal or exceed the Coast FIRE number, the model says they could reach the retirement target without further contributions. It does not say you can withdraw now or stop earning income for current expenses.
Worked Coast FIRE example
A 35-year-old wants $60,000 a year at age 65, uses a 4% withdrawal rate, expects a 7% nominal return, 2.5% inflation and 0.2% annual fees.
Retirement target$1,500,000
Years to grow30
Estimated real return4.2%
Coast number todayAbout $437,000
With $100,000 already invested, this person has not reached Coast FIRE under the base assumptions. Continuing to invest $500 per month improves the trajectory, but changing the savings rate, retirement age or spending target may still be necessary. The live result above calculates the exact figures from the current inputs.
What your result means
Already coasting
Your invested balance is at or above today’s coast number. Additional saving can add resilience, support earlier retirement or fund higher spending.
Not there yet
Your balance is below the current threshold. The result shows the gap and estimates when continued monthly contributions may close it.
No coast date
Under the entered assumptions, contributions do not meet the target by retirement. Consider saving more, spending less, retiring later or revisiting assumptions.
Assumptions that can change the answer
Market and planning inputs
- Returns vary and can arrive in an unfavorable sequence.
- Inflation for your personal expenses may differ from CPI.
- Fees reduce the capital left to compound.
- Asset allocation generally changes as retirement approaches.
Life and retirement inputs
- Taxes and health-care costs may not be included in spending.
- Social Security, pensions and other income can reduce portfolio withdrawals.
- Retirement length and spending flexibility affect withdrawal needs.
- Job changes and emergencies can interrupt contributions.
Educational projection, not financial advice. The tool uses smooth annualized growth and does not simulate market volatility, taxes, account rules, contribution limits, Social Security, pensions or required minimum distributions. No investment return or withdrawal rate is guaranteed.
Coast FIRE calculator FAQs
What is Coast FIRE?
Coast FIRE is the point where current retirement investments could grow to a chosen retirement target without additional contributions, assuming the entered return, inflation, fees and time horizon.
Does Coast FIRE mean I can stop working?
No. It typically means retirement saving may become optional in the model. You still need income to cover housing, food, insurance, taxes and other costs before retirement.
How is my Coast FIRE number calculated?
The retirement target is annual spending divided by the withdrawal rate. That future target is discounted to today using the estimated real return and years until retirement.
What investment return should I enter?
Use a cautious long-term expectation aligned with your portfolio, after considering fees. Because no forecast is reliable, compare the conservative, base and optimistic results rather than relying on one number.
Is a 4% withdrawal rate safe?
It is a common planning input, not a promise. A suitable rate depends on retirement length, portfolio mix, taxes, sequence of returns, fees and how flexibly you can change spending.
Why are results shown in today’s dollars?
Today’s dollars make the spending target and portfolio projection directly comparable. The calculator removes expected inflation through its real-return calculation.
Should Social Security or a pension reduce annual spending?
You can model portfolio-funded spending after reliable retirement income, but use conservative estimates and consider timing, taxes, eligibility and benefit uncertainty.
What if the calculator finds no coast age?
The entered assets and contributions do not reach the required threshold by retirement under the chosen assumptions. Try a higher contribution, later retirement age, lower spending target or more cautious review of all inputs.
Authoritative planning resources
These official resources help you examine compound growth, inflation and retirement timing beyond this simplified projection.
- SEC Investor.gov Compound Interest Calculator — official educational resource for contributions and compound growth.
- U.S. Bureau of Labor Statistics Consumer Price Index — official inflation measures and methodology.
- Social Security Administration retirement planning — benefit timing and planning information.