Compound Interest Calculator
Compound interest pays you twice: on the money you put in, and on the interest it has already earned. Give it a few years and the balance starts climbing on its own.
Enter a starting amount, a rate, and a time frame. Add a monthly contribution if you like. You get your projected balance, and exactly how much of it is interest.
Investment details
Estimated yearly return, before inflation.
Optional. Spread across your compounding schedule.
Your projection
- Projected future value
- $144,572.72
- Total interest
- $86,572.72
- Starting amount
- $10,000.00
- Total contributions
- $48,000.00
2.5× growth: the $58,000.00 you put in becomes $144,572.72
How your balance grows, year by year
Over 20 years you put in $58,000.00 and it grows to $144,572.72. $86,572.72 of that is interest. Interest earned overtakes the money you put in around year 16.
Year-by-year projected balance
| Year | Balance | You put in | Interest |
|---|---|---|---|
| 1 | $13,201.42 | $12,400.00 | $801.42 |
| 2 | $16,634.27 | $14,800.00 | $1,834.27 |
| 3 | $20,315.28 | $17,200.00 | $3,115.28 |
| 4 | $24,262.39 | $19,600.00 | $4,662.39 |
| 5 | $28,494.83 | $22,000.00 | $6,494.83 |
| 6 | $33,033.24 | $24,400.00 | $8,633.24 |
| 7 | $37,899.74 | $26,800.00 | $11,099.74 |
| 8 | $43,118.03 | $29,200.00 | $13,918.03 |
| 9 | $48,713.55 | $31,600.00 | $17,113.55 |
| 10 | $54,713.58 | $34,000.00 | $20,713.58 |
| 11 | $61,147.34 | $36,400.00 | $24,747.34 |
| 12 | $68,046.20 | $38,800.00 | $29,246.20 |
| 13 | $75,443.79 | $41,200.00 | $34,243.79 |
| 14 | $83,376.14 | $43,600.00 | $39,776.14 |
| 15 | $91,881.93 | $46,000.00 | $45,881.93 |
| 16 | $101,002.60 | $48,400.00 | $52,602.60 |
| 17 | $110,782.60 | $50,800.00 | $59,982.60 |
| 18 | $121,269.60 | $53,200.00 | $68,069.60 |
| 19 | $132,514.70 | $55,600.00 | $76,914.70 |
| 20 | $144,572.72 | $58,000.00 | $86,572.72 |
Before you rely on this
Results are generic estimates using standard time-value-of-money formulas, the same math everywhere. Real-world figures depend on your country's tax rules, rounding, fees, and lender or product terms, which vary by jurisdiction. Treat this as a guide and confirm important numbers with a local professional.
How the compound interest calculation works
The future value comes from the standard formula A = P(1 + r/n)^(nt), extended to treat your contributions as an annuity. P is the principal, r the annual rate, n the number of compounding periods per year, and t the number of years.
Compounding frequency matters less than people think. Daily compounding earns slightly more than annual, but the rate and the time invested matter far more.
Tips
- Time beats timing. Starting five years earlier is usually worth more than a slightly higher rate.
- Reinvest interest and dividends. Money sitting on the side earns nothing.
- A small automatic monthly contribution looks trivial today. After twenty years it isn't.
Frequently asked questions
What is compound interest, in plain terms?
Interest paid on your original deposit plus all the interest it has already earned. You earn interest on interest, so the longer you wait, the faster the balance grows.
How often should interest compound?
Monthly or daily compounding earns a bit more than annual. The difference is small. What actually decides the final amount is the rate and how long you stay invested.
Does this calculator include monthly contributions?
Yes. Add a recurring contribution and the tool adds it every compounding period, earning interest right alongside your principal.