How to Calculate Your FIRE Number
7 min read · Updated September 26, 2026 · by Thomas M, Registered Investment Adviser (South Carolina)
FIRE — Financial Independence, Retire Early — is built on one calculation: the portfolio that covers your spending forever. This guide shows how to find that number, how long it takes to reach and how a savings rate decides the timeline.
The FIRE number
FIRE number = yearly spending ÷ withdrawal rate. At a 4% rate this is 25 × spending. Spending $40,000 a year needs $1,000,000.00; at 3.5% it needs $1,142,857.14.
Years to reach it
Use the real return, (1 + return) ÷ (1 + inflation) − 1, so everything is in today’s money. Starting with $100,000, saving $30,000 a year at 7% and 2% inflation takes 16 years, 11 months. Saving $45,000 a year shortens it to 13 years, 1 month.
Why savings rate beats returns
A higher savings rate does two jobs: it raises the amount you invest and it lowers the spending you must replace, which shrinks the FIRE number. That is why people who save half their income can retire in roughly 17 years regardless of market luck.
Coast FIRE
The Coast FIRE number is the sum that grows to your FIRE number by a traditional retirement age without further contributions. With 25 years to go: $302,280.31 (grows to your FIRE number in 25 years with no more saving).
Risks to plan for
- Long retirements: 4% was studied over 30 years.
- Sequence-of-returns risk: poor early returns do the most damage.
- Healthcare and tax costs.
Try the FIRE calculator with cautious and optimistic inputs.
Practice questions
Test yourself, then tap to check. Answers are calculated by the tools linked below.
- Spending $50,000 a year, with $150,000 saved, saving $40,000 a year at 7% and 2% inflation. What is the FIRE number and how long to reach it?
Show answer
Your FIRE number: $1,250,000.00 · Time to reach it: 15 years, 9 months
- A 40-year-old has $80,000, saves $800 a month, expects 6% growth and 2.5% inflation and retires at 65. What will the pot be worth in today’s money?
Show answer
Projected savings at retirement: $911,592.75 · In today’s money (inflation-adjusted): $491,704.55
- $5,000 at 5% compounded yearly for 15 years, no contributions.
Show answer
Future value: $10,394.64
Frequently asked questions
What is a FIRE number?
The portfolio at which a safe withdrawal rate covers your yearly spending.
What withdrawal rate should I use?
4% is the classic figure; 3–3.5% is more cautious for retirements of 40–50 years.
What is Coast FIRE?
Having enough invested that growth alone reaches your retirement target.
Does FIRE include a house?
Only investments that can be drawn on count; a home you live in does not generate spendable income.
Try it yourself
FIRE CalculatorFind your FIRE number and how many years until financial independence at your savings rate, plus your Coast FIRE number.Retirement CalculatorProject your retirement savings, see the income they could provide in today’s money and what you need to save to hit your goal.Compound Interest CalculatorSee how savings grow with compounding and regular contributions.Keep learning
How to Calculate Retirement Savings8 min readHow Compound Interest Works7 min readHow to Calculate Inflation5 min readReviewed by Thomas M, Registered Investment Adviser (South Carolina), who launched his own financial advisory firm in 2010. Spot a mistake? Tell us. See our editorial policy. Finance content is educational and not financial advice; see the disclaimer.