Investment
Rule of 72 Calculator
A quick mental-math estimate of how long it takes an investment to double at a given annual return.
Your details
%
Years to double (approx.)
6
At 12% annually, your money roughly doubles every 6.0 years (72 ÷ 12).
How this is calculated
Years to double ≈ 72 ÷ annual rate of return — a well-known approximation of the exact compound-interest doubling formula.
Frequently asked questions
How accurate is the Rule of 72?
It's a fast mental-math approximation, most accurate for rates between roughly 6–10%. For a precise figure, or for large rate changes, use the Compound Interest Calculator directly.
Does this work for inflation too?
Yes — the same rule estimates how quickly purchasing power halves at a given inflation rate, just interpreted in reverse.