← Blogby Marcell Almeida

How to calculate compound interest on savings

See how a starting balance plus monthly contributions grows over time with compound interest.

Compound interest is interest on interest — the reason starting early matters. The Compound Interest Calculator projects final balance, total contributed, and interest earned with optional monthly deposits.

Try it — set principal, rate, years, and monthly contribution

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How it works

  1. Starting amount — initial principal.
  2. Annual rate — expected annual return (use conservative estimates).
  3. Years — investment horizon.
  4. Monthly contribution — optional recurring deposit.

Compounding frequency

This calculator compounds monthly (12 times per year), which matches most savings accounts and is a reasonable approximation for index funds.

Pair with CAGR

After investing, use the CAGR Calculator to measure actual annualized return between two balance snapshots.

The How to calculate compound interest on savings is free, runs locally, and never sends your data to a server. More finance calculators at maratool.com.