How Long to Double Money at 9%
At 9% a year, money doubles in 8.0 years. The Rule of 72 says 8.0.
Doubles in
8.0 years
Quadruples in
16.1 years
Grows 8 times in
24.1 years
Rule of 72 estimate
8.0 years
What different amounts become
| Start | After 8.0 years | After 16.1 years | After 24.1 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 9%
| Years | $1,000 becomes | $10,000 becomes | Growth |
|---|---|---|---|
| 5 | $1,539 | $15,386 | 1.54x |
| 10 | $2,367 | $23,674 | 2.37x |
| 15 | $3,642 | $36,425 | 3.64x |
| 20 | $5,604 | $56,044 | 5.60x |
| 25 | $8,623 | $86,231 | 8.62x |
| 30 | $13,268 | $132,677 | 13.27x |
| 40 | $31,409 | $314,094 | 31.41x |
| 50 | $74,358 | $743,575 | 74.36x |
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 9% the shortcut is off by 0.0 years.