Compound Interest Calculator
Project savings growth with regular monthly contributions and your choice of compounding. It runs entirely in your browser — nothing you type is uploaded anywhere.
Your figures
Result
How this calculator works
Compounding means interest starts earning interest of its own. Enter a starting amount, a rate, a term and how often interest is added — yearly, quarterly, monthly, daily — and the calculator projects the final value. A monthly contribution field covers the way most people actually save: not one lump sum, but a habit. Contributions are treated as paid at the start of each month and converted to your chosen compounding frequency at the equivalent rate, so changing the frequency keeps the comparison fair.
Two levers dominate the result, and neither is the one people expect. The contribution's size matters less than how early it starts, because the earliest money compounds for the longest; and the rate matters less than the term for the same reason. Doubling the term more than doubles the growth, which is why the projections surprise people even at modest rates.
Good practice and limits
Treat the output as a projection, not a promise: it assumes one steady rate, no tax, no fees and no withdrawals. Real savings vehicles vary all four. Use the calculator to compare strategies against each other — start now versus later, this contribution versus that one — where the assumptions are the same on both sides and the comparison stays honest.