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// myloanmath

Compound Interest Calculator

See how a starting amount — plus optional monthly contributions — grows over time with compound interest.

Future value
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How compound interest is calculated here

This calculator uses the standard compound interest formula A = P(1 + r/n)^(nt) for your starting amount, plus the future-value-of-an-annuity formula for any regular monthly contributions you add on top. More frequent compounding (daily vs. annually) produces a slightly higher return at the same stated interest rate — that's why the compounding frequency option matters.

Frequently asked questions

Does adding monthly contributions actually make a big difference?

Often more than the starting amount does over long time horizons — consistent contributions compound alongside your principal. Try comparing the result with and without a contribution to see the gap.

What compounding frequency should I choose?

Match what your actual account uses — most savings accounts and investment accounts compound daily or monthly. Annual compounding is mostly for simple illustrative comparisons.

Is this the same as an investment return calculator?

Conceptually yes — this models any growth process where interest is calculated on an increasing balance, which covers both savings accounts and investment growth.