Wealthy PotRule of 72 Calculator
How long does it take to double your money? Compare the rule of 72 with the exact answer for any interest rate or return, see what rate doubles money in a set number of years, and how inflation halves it.
How the rule of 72 works
Divide 72 by the yearly rate to get the years it takes money to double. At 8% a year: 72 / 8 = 9 years. To find the rate that doubles money in a set time, divide 72 by the years: doubling in 10 years takes about 7.2% a year. The calculator shows the shortcut next to the exact answer, for yearly, monthly, daily or continuous compounding.
Doubling time at common rates
| Rate per year | Rule of 72 | Exact (yearly compounding) | Exact (monthly compounding) |
|---|---|---|---|
| 1% | 72.0 years | 69.66 years | 69.34 years |
| 2% | 36.0 years | 35.00 years | 34.69 years |
| 3% | 24.0 years | 23.45 years | 23.13 years |
| 4% | 18.0 years | 17.67 years | 17.36 years |
| 5% | 14.4 years | 14.21 years | 13.89 years |
| 6% | 12.0 years | 11.90 years | 11.58 years |
| 7% | 10.3 years | 10.24 years | 9.93 years |
| 8% | 9.0 years | 9.01 years | 8.69 years |
| 9% | 8.0 years | 8.04 years | 7.73 years |
| 10% | 7.2 years | 7.27 years | 6.96 years |
| 12% | 6.0 years | 6.12 years | 5.81 years |
| 15% | 4.8 years | 4.96 years | 4.65 years |
| 20% | 3.6 years | 3.80 years | 3.49 years |
| 25% | 2.9 years | 3.11 years | 2.80 years |
What the rule says about your money
- Stocks: US stocks returned 6.95% a year after inflation from 1871 to 2023 (Shiller data, dividends reinvested). At that rate, buying power doubles about every 10.3 years.
- Bonds: 10-year Treasuries returned 2.44% a year after inflation over the same period, doubling buying power about every 28.8 years.
- Inflation: consumer prices rose 2.53% a year on average from 2000 to 2025 (BLS CPI-U). At that pace prices double, and a dollar buys half as much, in about 27.7 years. See the inflation calculator.
- Debt: a credit card balance at 24% APR compounded monthly doubles in 2.92 years if you pay nothing. Our debt payoff calculator shows how to get ahead of it.
Returns in real life change every year, so the rule describes an average path, not a promise. For growth with regular deposits, use the compound interest calculator.
Rate needed to double your money
| Double in | Rule of 72 | Exact rate (yearly compounding) |
|---|---|---|
| 3 years | 24.00% | 25.99% |
| 5 years | 14.40% | 14.87% |
| 7 years | 10.29% | 10.41% |
| 10 years | 7.20% | 7.18% |
| 12 years | 6.00% | 5.95% |
| 15 years | 4.80% | 4.73% |
| 20 years | 3.60% | 3.53% |
| 25 years | 2.88% | 2.81% |
| 30 years | 2.40% | 2.34% |
Tripling takes longer: about 16.2 years at 7%, against 10.2 years to double.
About the data
Doubling times are exact calculations (ln 2 divided by the compounding growth rate). Stock and bond returns: Robert J. Shiller's data, S&P Composite and 10-year Treasury real total returns, 1871-2023. Inflation: BLS CPI-U annual averages, 2000 and 2025. For general information, not investment advice.
Frequently Asked Questions
What is the rule of 72?
A shortcut for how long money takes to double at a fixed yearly growth rate: divide 72 by the rate. At 6% a year, money doubles in about 72 / 6 = 12 years. It works for anything that compounds: investments, savings, debt and prices rising with inflation.
How accurate is the rule of 72?
Very close for everyday rates. It is almost exact at about 7.8% a year (72 / 8 = 9 years against an exact 9.01). At lower rates it slightly overstates the time (4%: 18 years against 17.67) and at higher rates it understates it (12%: 6 years against 6.12).
What is the formula for exact doubling time?
Years = ln(2) / ln(1 + r), where r is the yearly rate as a decimal and the interest compounds once a year. With continuous compounding it is ln(2) / r, which is where the rule of 69.3 comes from.
What is the difference between the rule of 72, 70 and 69.3?
They are the same idea with different numerators. 69.3 is exact for continuous compounding, 70 is easy to divide and close at low rates such as inflation, and 72 is the most accurate for yearly compounding at typical investment returns, and divides evenly by 2, 3, 4, 6, 8, 9 and 12.
How long does it take to triple your money?
Divide about 114 by the rate as a rough guide, or use years = ln(3) / ln(1 + r). At 7% a year, money triples in 16.2 years.
Is the rule of 72 the same as the 72(t) rule?
No. 72(t) refers to section 72(t) of the tax code: taking IRA or retirement-plan withdrawals as a series of substantially equal periodic payments, one of the exceptions to the 10% additional tax on early distributions (IRS). It has nothing to do with doubling time.
