Looking for a compound interest calculator with monthly deposits? This free tool gives you year-by-year balance growth with regular monthly contributions. Just enter your numbers and press Calculate — results are instant.
Compound interest means you earn interest on your interest: every month (or day, or quarter — you choose how often it compounds) the balance grows by the rate, and the next month's interest is worked out on that bigger balance. Regular monthly contributions make the effect much stronger, because each new contribution also starts earning. That is why the balance grows slowly at first and then much faster in the later years.
Example: Initial investment $10,000 · Monthly contribution $200 · Annual rate 7% · 20 years · Compounded monthly
End Balance: $144,572.72
More often is slightly better, because each compounding adds interest sooner. The difference between monthly and yearly compounding is small at low rates and bigger at high rates — try changing the frequency to see it.
Yes, more than almost anything else. Because growth compounds, money invested ten years earlier has ten extra years of growth on growth. Even small monthly contributions become large over 20 or 30 years.
No. The rate you enter is an assumption. Real investments go up and down, so try a lower rate too — for example 5% instead of 7% — to see a more cautious outcome.