Compound Interest Calculator

How is compound interest calculated here?

The calculator grows your initial deposit at the annual interest rate, applying it at your chosen compounding frequency (annually, semi-annually, quarterly, monthly, or daily), and adds your regular contributions on top — so each period's interest is earned on a larger and larger balance.

What does contributions at start vs. end of period mean?

Start of period adds each contribution before that period's interest is applied, so it earns one extra period of growth; end of period adds it afterward. Start-of-period yields a slightly higher final balance.

What do the final balance, contributions, and interest figures show?

Final balance is everything you end with, total contributions is your deposits plus all recurring additions, and interest earned is the difference — the year-by-year breakdown shows how each year builds on the last.

Example: $10,000 at 7% for 20 years

Starting with $10,000, adding $100 monthly at 7% compounded monthly for 20 years, the balance grows to roughly $92,000 — of which about $34,000 is what you put in and the rest is compound interest. All math runs in your browser; nothing is uploaded.