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Once a week: 5 things worth your time.
1 story, 1 idea, 1 discovery, 1 tool, 1 book.
The Humanevi newsletter
Once a week: 5 things worth your time.
1 story, 1 idea, 1 discovery, 1 tool, 1 book.
See how a starting amount plus monthly contributions can grow, with the assumptions shown up front.
Final balance
$100,857
Total contributed
$65,000
Total interest earned
$35,857
| Year | Contributed | Interest earned | Balance |
|---|---|---|---|
| 1 | $11,000 | $617 | $11,617 |
| 2 | $17,000 | $1,763 | $18,763 |
| 3 | $23,000 | $3,481 | $26,481 |
| 4 | $29,000 | $5,817 | $34,817 |
| 5 | $35,000 | $8,819 | $43,819 |
| 6 | $41,000 | $12,541 | $53,541 |
| 7 | $47,000 | $17,042 | $64,042 |
| 8 | $53,000 | $22,382 | $75,382 |
| 9 | $59,000 | $28,629 | $87,629 |
| 10 | $65,000 | $35,857 | $100,857 |
This is an educational projection, not investment advice or a guarantee of returns. Real returns vary and this tool does not recommend any specific investment.
Converts a monthly rate into its yearly equivalent (and back) using compound interest.
Equivalent rate
12.68%
A simple calculation with the values you enter; check the specific rules for your case.
A mental shortcut to estimate years to double at a yearly rate.
By the rule of 72
9.0 years
Exact calculation
9.0 years
An estimate with compound interest and a constant rate; real returns vary and carry taxes and costs.
The compound interest calculator projects how a starting amount plus monthly contributions grows over the years at an annual rate you choose. It shows final balance, total contributed and interest earned, with a year-by-year table. It suits anyone who wants to see the effect of time and consistency when saving.
You enter an initial amount, a monthly contribution, an annual interest rate and a number of years. The annual rate is treated as effective and converted to an equivalent monthly rate by raising (1 + rate) to the power of 1/12 and subtracting 1, instead of dividing by 12. Month by month, the balance is multiplied by (1 + monthly rate) and the contribution is added. At the end of each year, the table records total contributed, interest and balance.
An initial amount of $5,000, a contribution of $300 a month, a rate of 10% a year for 10 years. Total contributed is 5,000 + 300 × 120 = $41,000. The final balance comes to about $72,928, which means roughly $31,928 in interest. The rate is your assumption, not a forecast of returns.
This is an educational projection, not investment advice or a guarantee of returns. A fixed rate does not exist in practice, and the math ignores taxes, fees and inflation. No specific investment product is recommended.
