What is Coast FIRE?
Coast FIRE is the point where the money you have already invested is enough to grow into your full retirement pot on its own. You still work and pay your bills, but you no longer need to put anything more aside for retirement. Your investments “coast” the rest of the way.
FIRE stands for Financial Independence, Retire Early. Full FIRE means saving enough to stop working altogether. Coast FIRE is a gentler milestone: you keep earning, but every rupee, dollar or pound you earn after that point can go to living, not saving.
Your Coast FIRE number is how much you need invested today for that to work. It depends on four things:
- how much you will spend each year in retirement,
- how much of that a pension or Social Security will cover,
- how fast your investments grow after inflation,
- and how many years are left until you retire.
That is what a Coast FIRE calculator is for. A general retirement calculator asks how much you will have at 65. A Coast FIRE calculator asks a different question: how much do you need invested now, and at what age can you stop saving for retirement altogether?
For example, a couple aged 30 who will spend $60,000 a year at 65, with $20,000 a year from pensions, needs their investments to pay $40,000 a year. At a 4% withdrawal rate that is a $1,000,000 pot. With 7% growth and 3% inflation, $263,555 invested today grows to that $1,000,000 by 65 without another dollar added. That $263,555 is their Coast FIRE number.
The Coast FIRE calculator formula
The maths fits in three steps, all in today’s money:
- Pot needed at retirement = (yearly spending − yearly pension) ÷ withdrawal rate
- Real growth = (1 + growth) ÷ (1 + inflation) − 1
- Coast FIRE number = pot needed ÷ (1 + real growth) ^ years until retirement
For the couple above that is $40,000 ÷ 0.04 = $1,000,000, then 1.07 ÷ 1.03 − 1 = 3.88%, then $1,000,000 ÷ 1.0388^35 = $263,555. Some calculators use growth minus inflation (4%) instead of real growth, which overstates your growth a little every year. Every formula and default is explained on the methodology page.
How to use this free Coast FIRE calculator
The calculator is free, needs no sign-up and keeps your numbers in your own browser.
- Choose your country. This sets your currency, how numbers are written, a default inflation rate and the name of your state pension. Taxes are not calculated for any country yet.
- Choose Just me or Couple. For a couple, enter money as household totals. The plan uses your age.
- Enter what you have invested and what you add each month. Include retirement accounts, index funds and other long-term investments. Leave out your home and your emergency fund.
- Enter when you want to retire and what you will spend each year. Use today’s money. The calculator handles inflation for you.
- Enter your pension income per year. If you are not sure, enter 0. That is the cautious choice.
Your answer updates as you type. The navy card shows your Coast FIRE number, how far along you are, the age you can stop saving and one honest next step.
Then move to Plan to test changes with sliders, Track to check in once a month, and Share to make an image of a milestone. Your numbers stay in your browser. Nothing is sent to us.
If you want to change the assumptions, press Change next to “Growth · Inflation · Withdrawal”. Every step of the maths is shown under “How we calculated this”, filled in with your own numbers.
A Coast FIRE calculator for couples
Most Coast FIRE calculators assume one person. Real households usually have two incomes, two sets of retirement accounts and sometimes two pensions.
This calculator treats a couple as one household. Add both of your investments together, both of your monthly contributions together and both pensions together. Enter the spending you expect as a household in retirement, which is usually less than double what one person would spend.
The ages used are yours. If your partner is several years older or younger, try the calculation with each of your ages. The difference shows how much the timing matters. A couple who reaches Coast FIRE often has a choice that a single person does not: one partner can step back from work, switch to part-time or take a career break while the other keeps working.
Coast FIRE calculator with a pension or Social Security
A pension makes your Coast FIRE number much smaller, because your investments only need to cover the gap between what you spend and what the pension pays. That is why a Coast FIRE calculator with Social Security or a pension built in gives a far more realistic answer than one that leaves it out.
In the example above, the couple spends $60,000 a year. Without a pension, they would need $1,500,000 at 65 and $395,332 invested today. With $20,000 a year from pensions, they need $1,000,000 at 65 and only $263,555 today. The pension cuts their Coast FIRE number by a third.
Enter pensions in today’s money and only include income you are confident about. In the US that is usually Social Security. In the UK it is the State Pension. In Canada it is CPP and OAS, and in Australia the Age Pension. Add any work pension that pays a set income.
If your pension starts later than your retirement age, this calculator does not yet handle the gap years. Enter a lower pension figure to stay on the safe side.
What makes the best Coast FIRE calculator?
The best Coast FIRE calculator is the one that fits your real situation and shows its working. Look for one that:
- handles couples, not just one person,
- takes a pension or Social Security into account,
- uses real growth, not growth minus inflation,
- works in your own currency,
- shows every step of the maths so you can check it,
- and keeps your numbers private.
This calculator was built to do all six. Whichever retirement Coast FIRE calculator you use, treat the answer as an estimate and test it against a cautious growth rate too.
Using it outside the US
The calculator works in thirteen places: the United States, the United Kingdom, Canada, Australia, India, the euro area, the United Arab Emirates, Japan, Saudi Arabia, Taiwan, Hong Kong, Singapore and Malaysia. Choosing your country sets the currency, the way large numbers are written (India uses lakhs, so ₹2,63,555), a default inflation rate and the name of the state pension.
The maths is the same everywhere. What changes is the inflation you expect and the growth you assume. If your country’s inflation is usually higher, your real growth is lower and your Coast FIRE number goes up. You can change growth, inflation and the withdrawal rate at any time with the Change button.
Two cautions. Taxes are not included for any country, so treat the result as a before-tax estimate. And the 4% withdrawal rate comes from US research; some people outside the US choose 3% or 3.5% to be safer.