How Long to Double Money at 7%
At 7% a year, money doubles in 10.2 years. The Rule of 72 says 10.3.
Doubles in
10.2 years
Quadruples in
20.5 years
Grows 8 times in
30.7 years
Rule of 72 estimate
10.3 years
What different amounts become
| Start | After 10.2 years | After 20.5 years | After 30.7 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 7%
| Years | $1,000 becomes | $10,000 becomes | Growth |
|---|---|---|---|
| 5 | $1,403 | $14,026 | 1.40x |
| 10 | $1,967 | $19,672 | 1.97x |
| 15 | $2,759 | $27,590 | 2.76x |
| 20 | $3,870 | $38,697 | 3.87x |
| 25 | $5,427 | $54,274 | 5.43x |
| 30 | $7,612 | $76,123 | 7.61x |
| 40 | $14,974 | $149,745 | 14.97x |
| 50 | $29,457 | $294,570 | 29.46x |
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 7% the shortcut is off by 0.0 years.