Compound Interest Calculator — Growth & Returns
A compound interest calculator shows how your savings grow when interest earns interest. Enter a starting amount, interest rate, time and monthly contributions to see your final balance, total interest and growth year by year.
Growth year by year
| Year | Balance | Interest that year |
|---|---|---|
| Year 1 | $11,962 | $762 |
| Year 2 | $14,066 | $904 |
| Year 3 | $16,322 | $1,056 |
| Year 4 | $18,741 | $1,219 |
| Year 5 | $21,336 | $1,394 |
| Year 6 | $24,117 | $1,582 |
| Year 7 | $27,100 | $1,783 |
| Year 8 | $30,298 | $1,998 |
| Year 9 | $33,728 | $2,230 |
| Year 10 | $37,405 | $2,477 |
How it works
- Enter your starting amount, yearly interest rate and how many years you will save.
- Choose how often interest compounds, and add a monthly contribution if you save regularly.
- See your final amount, total interest earned and a year-by-year growth table.
Formula
Worked example
Save $10,000 at 7% interest, compounded monthly, for 10 years, adding $100 a month. The final balance is $37,405.09 — your $22,000 of contributions plus $15,405.09 of interest. Without the monthly contributions, the same $10,000 would grow to $20,096.61.
Frequently asked questions
How does compound interest work?
Interest is added to your balance, then future interest is calculated on the bigger balance. Over years this snowball effect makes a large difference — that is why starting early matters so much.
What is the compound interest formula?
A = P(1 + r/n)^(nt). P is the starting amount, r is the yearly rate as a decimal, n is how many times a year interest compounds, and t is the number of years. Monthly contributions are added on top.
How much will $10,000 grow to in 10 years at 7%?
Compounded monthly with no extra contributions, $10,000 at 7% grows to $20,096.61 in 10 years. Adding $100 a month takes it to $37,405.09.
Does compounding frequency matter?
Yes, but only a little. Monthly compounding earns slightly more than yearly compounding at the same rate, because interest starts earning interest sooner. The rate and the time matter far more.
What is the difference between simple and compound interest?
Simple interest is only paid on the original amount. Compound interest is paid on the amount plus all interest earned so far, so it grows faster over time.
How much should I save each month?
It depends on your goal and income, but even $100 a month adds up: at 7% over 10 years it contributes $12,000 and earns extra interest on top. The calculator shows the effect of any monthly amount.