Estimate your FIRE number
The 25× rule says you need 25 times annual spending — this shows the target and how many years to reach it.
Tools used in this guide
The job
Financial independence means investments cover spending forever. The classic shortcut sets the target at spending ÷ withdrawal rate — 4 % gives the famous 25×. The second half of the question is the timeline: how long until your savings rate gets there.
Spending, savings, rate, return
Enter annual spending, current investments, yearly saving, a withdrawal rate (4 % default), and an expected real return. The output is the target plus the compounding years to reach it.
Worked example
Spending 40,000 a year at 4 % needs 1,000,000. Starting from 100,000 and saving 20,000 a year at 5 % real return lands you there in about 21 years. Halve the spending and the target halves to 500,000 — at the same 20,000 saving pace the timeline drops to about 12 years, faster than linear because the goal shrank while contributions did not.
Where it stops
Constant real return is a smoothing fiction — real markets swing, and sequence-of-returns risk is the biggest failure mode of the 4 % rule. Taxes, pensions, and lifestyle changes are outside the model.