Interest Calculators
Compound Interest Calculator
Compounding means interest is added to the balance and then earns interest itself. Enter a starting amount, an optional monthly contribution and a rate to see the projected balance year by year.
Projected balance
$148,612
- Total you put in
- $70,000
- Interest earned
- $78,612
- Growth multiple
- 2.12×
Growth accelerates because each year's interest earns interest of its own.
Year-end balances
| Year | Balance |
|---|---|
| 1 | $13,701 |
| 2 | $17,630 |
| 3 | $21,801 |
| 4 | $26,229 |
| 5 | $30,931 |
| 6 | $35,923 |
| 7 | $41,222 |
| 8 | $46,849 |
| 9 | $52,822 |
| 10 | $59,164 |
How this calculator works
A = P × (1 + r ÷ m)^(m × t) + contributions compounded monthly
- A
- the projected balance at the end
- P
- the starting amount
- r
- the annual rate of return, as a decimal
- m
- how many times a year interest compounds
- t
- the number of years invested
Regular contributions are added at the end of each month and compound from that point on.
Example calculation
Illustrative example — not advice
If you start with $10,000, add $250 a month and earn 6% a year for 20 years
- 01You contribute $10,000 up front plus $60,000 over the twenty years.
- 02Monthly compounding at 6% turns that into roughly $148,000.
About $148,000, of which around $78,000 is growth rather than money you paid in.
Most of the growth arrives in the final third of the period, which is why time in the market matters more than timing it. This is an illustrative example, not a projection of any specific product.
Important considerations
- Investment returns vary year to year; a single average rate smooths over real volatility.
- Fees, taxes and inflation all reduce the real value of the final balance.
- A guaranteed savings rate and an expected investment return are not the same kind of number.
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Learn more
Terms used here
Frequently asked questions
Does compounding frequency make much difference?
Less than most people expect. Moving from annual to monthly compounding at 6% adds only a fraction of a percent a year. The rate, the contribution and the time horizon matter far more.
Should I adjust for inflation?
If you want the result in today's money, enter a real return — the expected return minus expected inflation — instead of the nominal rate.
Disclaimer
Calculator results are estimates for informational purposes only and may differ from actual rates, fees, taxes, terms or a lender's own calculations. Legamoney does not provide financial advice.
Last reviewed 2026-08-01