Rule of 72 Calculator
A quick mental-math shortcut: at X% return, your money doubles in roughly 72 ÷ X years.
Inputs
How it works
The rule of 72 is an approximation: ln(2) ≈ 0.693, and 72 is a friendly close-enough numerator for typical rates.
Frequently asked questions
Are these returns guaranteed?
No — projections assume your inputs hold steady. Real markets fluctuate; treat results as planning estimates.
What's a reasonable long-term return?
Diversified U.S. stock portfolios have averaged 7–10% before inflation over the long run.
Should I include inflation?
Yes if you care about purchasing power. Use a real return = nominal return − inflation rate.
Do taxes affect this?
Inside tax-advantaged accounts (401k, IRA, HSA) growth is tax-deferred or tax-free. Taxable accounts pay annual tax on distributions and on gains when sold.
Does dollar-cost averaging help?
It smooths timing risk and is a behavioral win even if a lump-sum invested earlier has higher expected return.