Compound Interest Calculator
Enter a starting amount, an annual interest rate and a time span to see the final balance, how much of it is interest, and a table of every year along the way. Add a monthly contribution to model regular saving.
| Year | Deposits | Interest | Balance |
|---|---|---|---|
| 1 | 2,200.00 | 79.05 | 2,279.05 |
| 2 | 3,400.00 | 223.53 | 3,623.53 |
| 3 | 4,600.00 | 436.81 | 5,036.81 |
| 4 | 5,800.00 | 722.38 | 6,522.38 |
| 5 | 7,000.00 | 1,083.97 | 8,083.97 |
| 6 | 8,200.00 | 1,525.44 | 9,725.44 |
| 7 | 9,400.00 | 2,050.90 | 11,450.90 |
| 8 | 10,600.00 | 2,664.64 | 13,264.64 |
| 9 | 11,800.00 | 3,371.17 | 15,171.17 |
| 10 | 13,000.00 | 4,175.24 | 17,175.24 |
About this tool
Compound interest pays interest on interest: each period's interest is added to the balance, so the next period earns a little more. The formula for a single deposit is A = P × (1 + r/n)^(n×t), where r is the annual rate, n the number of compounding periods per year and t the years. This calculator simulates every period instead, so regular contributions are handled exactly.
Frequency matters less than people expect. At 5%, compounding monthly instead of yearly adds only about 0.12% a year. Time and regular deposits matter far more: 100 a month for 30 years at 6% grows to roughly 100,000, of which only 36,000 was paid in.
Frequently asked questions
- What is the difference between simple and compound interest?
- Simple interest is paid only on the original deposit. Compound interest is also paid on interest already earned, so the balance grows faster the longer it is left.
- When are the monthly contributions added?
- At the end of each compounding period, converted to match the frequency you choose. With monthly compounding that is exactly one contribution per month.
- Does the calculator account for tax or inflation?
- No. The figures are gross. To estimate real growth, subtract the expected inflation rate from the interest rate before calculating.
- What is the rule of 72?
- A quick estimate of doubling time: divide 72 by the annual rate. At 6%, money doubles in about 12 years.