How Long to Double Money at 1%
At 1% a year, money doubles in 69.7 years. The Rule of 72 says 72.0.
Doubles in
69.7 years
Quadruples in
139.3 years
Grows 8 times in
209.0 years
Rule of 72 estimate
72.0 years
What different amounts become
| Start | After 69.7 years | After 139.3 years | After 209.0 years |
|---|---|---|---|
| $1,000 | $2,000 | $4,000 | $8,000 |
| $5,000 | $10,000 | $20,000 | $40,000 |
| $10,000 | $20,000 | $40,000 | $80,000 |
| $25,000 | $50,000 | $100,000 | $200,000 |
| $50,000 | $100,000 | $200,000 | $400,000 |
| $100,000 | $200,000 | $400,000 | $800,000 |
Growth over time at 1%
| Years | $1,000 becomes | $10,000 becomes | Growth |
|---|---|---|---|
| 5 | $1,051 | $10,510 | 1.05x |
| 10 | $1,105 | $11,046 | 1.10x |
| 15 | $1,161 | $11,610 | 1.16x |
| 20 | $1,220 | $12,202 | 1.22x |
| 25 | $1,282 | $12,824 | 1.28x |
| 30 | $1,348 | $13,478 | 1.35x |
| 40 | $1,489 | $14,889 | 1.49x |
| 50 | $1,645 | $16,446 | 1.64x |
How it is worked out
Years to double = ln(2) / ln(1 + r)
ln = natural logarithm, r = rate as a decimal.
The Rule of 72 is the shortcut version. Divide 72 by the rate.
At 1% the shortcut is off by 2.3 years.