Coast FIRE calculator

How the Coast FIRE calculator works

Coast FIRE turns one question around. Instead of “how much do I need to stop working?”, it asks: “how much do I need invested today so that I never have to add another euro for retirement?” Compound growth does the rest.

The calculator works in three steps, all in today’s money:

1. Your retirement target. Monthly spending in retirement minus your expected pension, times 12, divided by the withdrawal rate. With 3.5 %, every €1,000 of monthly spending not covered by the pension needs about €343,000.
2. Your coast number. The target discounted to today at the real return (return after inflation):

Coast number = Target ÷ (1 + real return)^{years to retirement}

3. Your coast age. Your current investments plus your monthly saving, projected month by month. The first month they reach that month’s coast number is the day you can stop saving for retirement.

The coast number rises every year, because there is one year less to grow. Your savings rise faster while you keep adding to them. Where the two lines cross, you can stop.

Example: Lena and Jonas, 34

Lena and Jonas want to spend €3,700 a month in retirement and expect €1,400 of pension from 67. Their portfolio has to pay the other €2,300, so their target is €788,571. At 6% return and 2% inflation (about 3.9% real), their coast number today is €221,592.

They have €24,000 and save €1,250 a month. They reach Coast FIRE at 52, with €450,004 invested. If they stop saving then, that money grows to €788,652 by 67 without another deposit. Everything they earn after 52 can go to living, not saving.

The pension does a lot of the work. Without it, the target would be €1,268,571 and the coast number today €356,473; at their current saving they wouldn’t reach it before 67.

Coast FIRE number by age

How much you need invested today depends mostly on how many years your money has to grow. For the same target of €788,571 at 67 and 3.9% real return:

Your age today	Coast number
25	€156,748
30	€189,990
35	€230,281
40	€279,118
45	€338,311
50	€410,057

Money invested at 25 has more than four decades to grow; at 50 it has 17 years. That is why Coast FIRE is mostly a plan for people in their twenties and thirties.

Coast FIRE or Barista FIRE?

Both are about working less before full retirement, but they ask different things of your portfolio.

• Coast FIRE: your investments are left alone until retirement. Work pays all of today’s spending. Switch to “Coast FIRE” above to see when you can stop saving.
• Barista FIRE: a part-time or lower-paid job pays part of your spending. Switch to “Barista FIRE” to see the income that job has to bring in from your coast age if you don’t touch the portfolio: in the example €3,700 a month after tax, 75% of today’s take-home pay.

In Germany tax and social contributions fall faster than gross pay, so the hours you need are usually lower than that share. The part-time calculator works out the net pay for fewer hours. Any income short of your spending has to come out of the portfolio, and that pushes your coast age back. The Coast FIRE vs Barista FIRE guide compares both in more detail.

Which return should I use?

A real one, because your target is in today’s money. The calculator asks for the nominal return and inflation and converts them. Over a few decades a broad global equity fund has returned around 7 % a year before inflation, with years far below and above that. A cautious 5–6 % leaves room for costs and bad decades. A single point less return can delay your coast age by years; try it with the “What if” buttons.

What it can’t see

Coasting means betting on the average return over decades, and a weak decade can leave you short, so recheck every few years. Working less also lowers the statutory pension you’ll get, which raises your target. Tax on withdrawals and health insurance in retirement come on top. And life before retirement may need the money you planned to leave alone. Zenarios models all of it in one plan, month by month, so you can see whether coasting still works after the next big decision. To go all the way, the FIRE calculator shows when you could stop working entirely.

Common questions

What is Coast FIRE?

Coast FIRE means you have invested enough that, without adding another euro, your portfolio grows to what you need by retirement. From then on, work only has to pay your current spending. You can take a lower-paid job, work fewer hours or simply stop saving for retirement.

How do I calculate my Coast FIRE number?

Divide your retirement target by (1 + real return) to the power of the years until retirement. A €750,000 target 25 years away at a 3 % real return gives €750,000 ÷ 1.03^25 = €358,204 today. The calculator first works out the target from your spending, pension and withdrawal rate.

What is the difference between Coast FIRE and Barista FIRE?

With Coast FIRE you leave your investments alone and your job pays all current spending. Barista FIRE usually means part-time work plus some withdrawals. This calculator's Barista view shows the income a lighter job must bring in if you don't touch the portfolio: in the example €3,700 a month after tax, 75 % of today's take-home pay.

Should I use a nominal or a real return?

A real one, because the target is in today's money. The calculator converts for you: a 6 % nominal return with 2 % inflation is about 3.9 % real. Mixing a nominal return with a target in today's prices overstates how far your savings get.

What if markets disappoint after I stop saving?

Then you arrive at retirement short. Coasting relies on the average return over decades, so it is worth checking again every few years. In the example, a return 1 point lower moves the coast age from 52 to almost 61.

Sources

• § 35 SGB VI: Regelaltersrente at 67 (gesetze-im-internet.de)
• AAII Journal (1998): Retirement Savings – Choosing a Withdrawal Rate That Is Sustainable

By Constantin Metz, the maker of Zenarios · Reviewed 25 October 2026. Results are estimates from your inputs and simplified rules, not financial, tax or legal advice. How Zenarios calculates