Compound Interest Calculator

Those tools amortize a debt — a fixed starting balance that shrinks to zero as you make payments; this tool does the opposite, projecting how a starting balance (plus optional ongoing contributions) grows over time as interest compounds, which is the situation for savings accounts, retirement accounts, or general investments.

It controls how often interest is calculated and added to the balance — monthly compounding applies interest 12 times a year at 1/12th the annual rate each time, while annual compounding applies it once a year at the full rate; more frequent compounding produces a very slightly higher final balance for the same nominal annual rate.

The total annual contribution (monthly amount × 12) is divided evenly across however many compounding periods occur per year, so contributions are always spread proportionally regardless of whether you've selected monthly, quarterly, annual, or daily compounding.

No — this is a straightforward compound-growth projection using a constant nominal rate; it doesn't model taxes, inflation, investment fees, or variable year-to-year returns, all of which would reduce real-world results compared to this estimate.

It isolates exactly how much of the final balance came from growth versus from money you actually put in, which makes the power (or limits) of compounding easy to see at a glance, especially over longer time horizons.