Rule of 72: time to double your money
How many years to double (or triple) an investment at a given return, and the reverse.
How it works
Rule of 72: years ≈ 72 / rate. Exact value: ln 2 / ln(1 + rate). Rate needed to double in n years = 2^(1/n) − 1.
Results are for guidance only and do not replace professional advice.
Worked example
With the default values:
- Annual return (%)6
- Or: double in how many years?10
you get:
- Your money doubles in11.9 years
- Rule of 72 (mental maths)12 years
- Triples in18.9 years
- × 10 in39.5 years
Frequently asked questions
How does the “Rule of 72: time to double your money” tool work?
Rule of 72: years ≈ 72 / rate. Exact value: ln 2 / ln(1 + rate). Rate needed to double in n years = 2^(1/n) − 1.
What do I need to enter?
Just fill in: annual return, or: double in how many years?. The result updates as you type.
Can you give an example?
Annual return (%): 6; Or: double in how many years?: 10 → Your money doubles in: 11.9 years; Rule of 72 (mental maths): 12 years.
Is this calculator free, and is my data private?
Yes. HOD Calc is completely free with no sign-up. The calculation runs in your browser: nothing you type is sent or stored.