FIRE calculator

How the FIRE calculator works

FIRE stands for financial independence, retire early: enough invested that work becomes optional. Most FIRE calculators divide your yearly spending by a withdrawal rate and stop there. That ignores the state pension, which for most people in Germany pays a large part of the bills from 67.

This calculator splits the years after work into two phases, all in today’s money:

Capital needed at age A = spending for every month from A to the pension + (spending − pension) × 12 ÷ withdrawal rate, discounted to A

1. The bridge. From the day you stop until the pension starts, your portfolio pays all your spending. The calculator adds up those months, discounted at your real return (the return after inflation, here 3.9%).
2. After the pension. From then, the portfolio only covers spending minus the pension, at the withdrawal rate you choose (default 3.5 %).
3. Your savings. What is left of your take-home pay after spending is invested at the end of each month and grows at the real return.

The calculator steps forward month by month and stops at the first month in which your capital reaches what you’d need to stop then. That month is your FI age.

Example: Lena and Jonas in Berlin

Lena and Jonas, both 34, take home €4,950 a month and spend €3,700. They save €1,250, a savings rate of 25%, and have €24,000 invested. They expect a joint pension of €1,400 a month from 67.

At 6% return and 2% inflation they can stop at 62 and 6 months with €846,990. Without the pension they’d need €1,268,571 and would get there at 70 and 2 months. The classic 4 % rule would put the number at €1,110,000.

The capital needed falls the closer you stop to the pension: €924,458 at 55, €875,332 at 60 and €788,571 from 67.

Why the pension lowers your FIRE number

Every euro of pension is a euro the portfolio doesn’t have to pay, for life. At a 3.5 % withdrawal rate, €100 of monthly pension replaces about €34,000 of capital. Lena and Jonas’s €1,400 replace €480,000 of the target.

The pension does not help before it starts. That is why stopping at 50 costs far more than the simple formula suggests: someone has to pay those 17 years in full. The retirement bridge calculator checks whether that money is actually available when you need it.

What savings rate do you need?

The savings rate matters more than the income. Starting from zero with €4,000 a month take-home pay, at the same return and inflation:

Savings rate	Years to FI, no pension	With €1,400 pension from 67
25%	38	29
40%	25	19
50%	19	14
65%	12	8

A higher savings rate works twice: more goes in, and you need less because you are used to spending less.

3.5 % or 4 %?

The 4 % rule comes from US research on retirements of up to 30 years, best known from the 1998 Trinity study. Early retirees need money for 40 or 50 years, pay tax on withdrawals and often hold more cash. Zenarios uses 3.5 %, and you can change it under “Assumptions”. To see how a rate holds up in bad markets, use the withdrawal calculator with its stress test.

What it can’t see

It assumes a steady return, while real markets swing, and a crash in the first years of withdrawals hurts most. It treats your pension as fixed, though stopping work early means fewer contribution years and a smaller pension. It leaves out tax on withdrawals and health insurance, which voluntary members of German public insurance pay on capital income too. And it doesn’t know about the child, the home or the sabbatical you are planning. Zenarios puts all of that into one month-by-month plan, including the years before and after the pension.

Common questions

How do I calculate my FIRE number?

The classic FIRE number is your annual spending divided by the withdrawal rate: 25 times at 4 %, about 28.6 times at 3.5 %. Spending €3,700 a month gives €1,110,000 at 4 % or €1,268,571 at 3.5 %. This calculator also counts your pension: with €1,400 a month from 67, the capital needed from 67 falls to €788,571, plus enough to pay the years before in full.

Why does a pension lower the FIRE number?

Once the pension starts, your portfolio only pays spending minus the pension. In the example that is €2,300 instead of €3,700 a month, which lowers the long-run target by €480,000 (€1,400 × 12 ÷ 3.5 %). Before the pension the portfolio pays everything, so the calculator adds those bridge years on top.

Is the 4 % rule safe for early retirement?

The 4 % rule comes from US studies of retirements up to 30 years, with US stock and bond returns and before tax. An early retirement can last 40 or 50 years, and in Germany withdrawals are taxed on their gain share. Zenarios uses 3.5 % by default. Test your own rate in the withdrawal calculator's stress test.

What savings rate do I need to retire early?

Starting from zero with €4,000 a month take-home pay, a 6 % return and 2 % inflation, and without counting a pension: saving 25 % takes about 38 years, 50 % about 19 years and 65 % about 12 years. A pension of €1,400 from 67 shortens each, to about 29, 14 and 8 years.

Which pension figure should I enter?

The pension you expect if you stop early, net and in today's money. A German Renteninformation assumes you keep paying in until the regular retirement age, so its figure is too high for an early exit. When in doubt, enter less.

Sources

• § 35 SGB VI: Regelaltersrente at 67 (gesetze-im-internet.de)
• § 240 SGB V: contributions of voluntary members of public health insurance
• 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