See roughly how long it takes to double your money at a given return — the handy Rule of 72, with the exact math alongside it.
The Rule of 72 is a mental-math shortcut; it's most accurate around 6–10%. The exact figure uses compound growth. Real returns vary and aren't guaranteed. General information, not investment advice.
Divide 72 by your annual rate of return and you get, roughly, the number of years for money to double. It's a fast sanity check — 8% doubles in about 9 years — and surprisingly close to the exact compound-growth answer.
Years to double ≈ 72 ÷ rate
Very close for rates around 6–10%. At very high or very low rates it drifts a little — the "exact years" result shows the true compound figure.
Yes — divide 72 by the inflation rate to see how fast prices double (and money's buying power halves).
Related: compound interest calculator · future value calculator · inflation calculator · all free calculators.
More free retirement & investing tools — no signup, works on any device.
Yes. The Rule of 72 Calculator is completely free, runs in your browser, and never asks for a signup, email, or download. Enter your numbers and the result updates instantly.
It uses standard formulas and recalculates the moment you change a value, so the math is exact for the inputs you enter. Treat the result as a reliable planning estimate; for decisions with legal or tax consequences, confirm the figures with a qualified professional.
Yes. The calculator is mobile-friendly and works on any phone, tablet, or computer — there is no app to install and nothing to save.
Yes. Scroll to “Add this free calculator to your site” above and copy the embed snippet to place the live calculator on your blog or website for free.
Last reviewed: September 2026. Free to use, no signup — Rule of 72 Calculator by ToolWise Digital.
Copy the snippet to embed the live calculator on your blog or website — free for any site. The small “Calculator by ToolWise Digital” credit line keeps it free; you're welcome to remove it, but we appreciate you leaving it.
Ready-made Google Sheets & Excel trackers for money, taxes, and small business — each with a free phone version.
Browse the shop →Subscribe and we'll email you our Simple Monthly Budget (Google Sheets & Excel, plus a phone version) — free. Then the occasional short note on pricing, bookkeeping, and the money side of a small business. No spam — unsubscribe anytime.