Rule of 72 Calculator

Estimate how fast money doubles at any interest rate — the classic Rule of 72.

Annual rate (%):

Or: years to double:

Estimates only — assumes a constant rate and no withdrawals.

How to use

Enter a rate or a time frame, then click Calculate. Everything runs in your browser — nothing is uploaded or stored.

What is the Rule of 72?

Years to double ≈ 72 ÷ interest rate. Fast mental math for compounding.

How accurate is it?

Close for rates 4–12%; we also show the exact logarithmic answer.

☕

Every tool runs 100% in your browser — no uploads, no signups. If a tool saved you time, consider supporting us with a small donation.