Coast FIRE Calculator
is your Coast FIRE number. You already have enough!
How to Use the Coast FIRE Calculator
To use the Coast FIRE calculator, enter 5 basic numbers, check 3 advanced settings, and read the result card. The whole process takes about 2 minutes.
- Enter current age: Use your age in whole years to set your investment time horizon.
- Set target retirement age: Choose the age you want portfolio withdrawals to start.
- Enter annual retirement spending: Estimate your yearly living expenses in today's money.
- Add current invested assets: Include 401(k), IRA, ISA, and taxable brokerage funds (exclude home equity).
- Enter monthly contribution: Input ongoing monthly savings to see how quickly you reach your coast age.
- Adjust advanced settings: Review return rate (default 7%), inflation (3%), and safe withdrawal rate (4%).
- Read your results: Check your Coast FIRE number, current progress percentage, and growth chart.
How Does the Coast FIRE Calculator Work?
The Coast FIRE calculator works in 4 steps: it converts your expected return into a real return, sets a FIRE target from your spending and withdrawal rate, discounts that target back to today, and compares the result with your current portfolio.
- Real return. The calculator strips inflation out of your growth rate: real return = (1 + nominal return) ÷ (1 + inflation) − 1. A 7% return with 3% inflation gives 3.88%. Every figure then stays in today's purchasing power.
- FIRE number. Annual spending divided by the withdrawal rate. $40,000 at a 4% safe withdrawal rate needs $1,000,000. The 4% rule traces back to William Bengen's 1994 research and the 1998 Trinity Study.
- Coast FIRE number. The FIRE number divided by (1 + real return) raised to your years until retirement. This is the present value of your future nest egg.
- Coast age. The calculator grows your balance year by year at the real return, adds 12 months of contributions each year, and finds the first age where your balance meets that year's coast threshold.
All math runs in your browser. Nothing you type is sent or stored.
This diagram reads your numbers from the calculator above. Change an input there and watch each step update. Tap a step for its math.
Coast FIRE Formula Explained
The Coast FIRE formula is Coast FIRE number = (Annual Expenses ÷ Withdrawal Rate) ÷ (1 + Real Return)Years to Retirement.
The formula has 4 variables:
- Annual expenses are your yearly retirement spending in today's money.
- Withdrawal rate is the share of the portfolio you take out each year. A 4% rate equals 25× expenses, 3.5% equals about 28.6×, and 3% equals about 33.3×.
- Real return is investment growth after inflation: (1 + nominal return) ÷ (1 + inflation) − 1.
- Years to retirement is your retirement age minus your current age.
Coast FIRE spreadsheet formula
Put annual expenses in B1, withdrawal rate in B2, nominal return in B3, inflation in B4, and years to retirement in B5, with the three rates formatted as percentages. Then paste this into Google Sheets or Excel:
=PV((1+B3)/(1+B4)-1, B5, 0, -(B1/B2)) Move a slider and the formula fills in with your numbers.
- FIRE number
- Real return
- Growth factor
- Coast FIRE number
Coast FIRE Calculation Example
A 30-year-old who wants $40,000 a year from age 65, using a 7% return, 3% inflation, and a 4% withdrawal rate, has a Coast FIRE number of $263,555.
Pick a country below to see the same math in dollars, pounds, and rand.
Maya is 30, plans to retire at 65, and wants $40,000 a year in today's money. Maya expects a 7% return, 3% inflation, and uses a 4% withdrawal rate.
- FIRE number$40,000 ÷ 0.04 = $1,000,000
- Real return1.070 ÷ 1.030 − 1 = 3.883%
- Years to retirement65 − 30 = 35
- Growth factor1.03883^35 = 3.7943
- Coast FIRE number$1,000,000 ÷ 3.7943 = $263,555
Oliver is 35, plans to retire at 67, and wants £28,000 a year in today's money. Oliver expects a 6.5% return, 2.5% inflation, and uses a 4% withdrawal rate.
- FIRE number£28,000 ÷ 0.04 = £700,000
- Real return1.065 ÷ 1.025 − 1 = 3.902%
- Years to retirement67 − 35 = 32
- Growth factor1.03902^32 = 3.4043
- Coast FIRE number£700,000 ÷ 3.4043 = £205,624
Thandi is 32, plans to retire at 65, and wants R360,000 a year in today's money. Thandi expects a 10% return, 5% inflation, and uses a 4% withdrawal rate.
- FIRE numberR360,000 ÷ 0.04 = R9,000,000
- Real return1.100 ÷ 1.050 − 1 = 4.762%
- Years to retirement65 − 32 = 33
- Growth factor1.04762^33 = 4.6421
- Coast FIRE numberR9,000,000 ÷ 4.6421 = R1,938,790
Our Financial Tools
Explore all our specialized Coast FIRE calculators — tailored by country and life stage.
Calculator
Frequently Asked Questions
Short, direct answers to the questions people ask most about Coast FIRE numbers, returns, inflation, and fees.
What is a Coast FIRE number?
It's the amount you need invested today so compound growth alone reaches your full retirement target by your retirement age.
How do I calculate my Coast FIRE number?
Divide your annual retirement spending by your withdrawal rate, then divide by (1 + real return) raised to your years until retirement.
Can I stop investing after reaching Coast FIRE?
Yes, you can stop retirement contributions once you reach Coast FIRE, as long as your return and spending assumptions hold and the money stays invested.
Does Coast FIRE mean I can stop working?
No — Coast FIRE secures your future retirement, but you still need income to cover current living expenses until retirement age.
What rate of return should I use?
A nominal return of 6%–7% with 3% inflation (real return of 3%–4%) is a conservative starting point for long-term planning.
How does inflation affect my Coast FIRE number?
Higher inflation lowers your real return and raises your Coast FIRE number — all figures in this calculator are shown in today's purchasing power.
Is Coast FIRE different from regular FIRE?
Yes — regular FIRE means you can stop working now (25× expenses saved), while Coast FIRE means your investments will grow to that amount by retirement age.
Can I reach Coast FIRE in my 30s?
Yes — time does most of the work, so your 30s are one of the easiest decades to hit Coast FIRE with consistent saving.
Does Coast FIRE account for investment fees?
Not automatically — subtract your total fees from your expected return before entering it into the calculator.