How Long Does It Take to Double Your Money?
The Rule of 72 gives the answer in seconds: divide 72 by your annual return.
At a 7% return, money doubles in about 10.3 years (72 ÷ 7). At 10% it is about 7.2 years. The Rule of 72 is a fast estimate that stays accurate across typical return ranges — but it assumes a single lump sum left to compound, with no contributions.
The Rule of 72, in one line
Divide 72 by your expected annual return (as a whole number) to get the approximate years to double:
Years to double ≈ 72 ÷ annual return %
Here is the full table, compared with the precise compounding math:
| Annual return | 72-rule estimate | Precise (ln2) |
|---|---|---|
| 3% | 24.0 years | 23.4 years |
| 5% | 14.4 years | 14.2 years |
| 7% | 10.3 years | 10.2 years |
| 8% | 9.0 years | 9.0 years |
| 10% | 7.2 years | 7.3 years |
| 12% | 6.0 years | 6.1 years |
The rule is within a few percent for the return ranges most investors care about — close enough for quick planning, exact enough to act on. Run the Rule of 72 calculator →
Small rate differences, huge time differences
Notice what a 2% change does: at 5% doubling takes 14.4 years; at 7% it takes 10.3; at 10% it takes 7.2. Over a working career, a few percentage points of extra return can cut years — or decades — off the doubling timeline. That is why real returns after inflation and fees matter so much.
The rule assumes compounding alone
The Rule of 72 applies to a single lump sum left to compound. If you keep adding contributions, the money doubles faster — the rule is a floor, not the whole story. See the exact doubling with compounding, and the Rule of 72 explained in depth.
Risk & limitations
- The Rule of 72 is an estimate, not a guarantee; returns vary and can be negative.
- It assumes pure compounding with no contributions, taxes or fees.
- Inflation reduces the real value of the doubled amount.
- Educational projection only, not personalized investment advice.
Sources: Long-run return context: NYU Stern (Damodaran) · Inflation data: U.S. Bureau of Labor Statistics CPI. Educational projection only.