Compound Interest Calculator

There's a well-known mental shortcut for this, the Rule of 72: divide 72 by your annual interest rate to get a rough estimate of how many years it takes your money to double. At 6% annual growth, that's roughly 12 years to double, a useful sanity check even when you'd rather let the actual calculator run the precise numbers.

Compounding frequency, whether interest calculates annually, monthly, or daily, has a smaller but real effect on your final balance. More frequent compounding means your money starts earning on previously earned interest slightly sooner, which adds up to a modestly higher effective return compared to the same stated rate compounded less often.

Enter your starting principal, a regular contribution amount, your expected annual rate, your compounding frequency, and your timeframe in years. The calculator outputs your ending balance along with a clear split between what you contributed and what grew from interest alone.

The exact same math that builds wealth works against you with debt, specifically revolving balances like credit cards, where unpaid interest compounds right alongside any new charges, which is worth remembering if you're ever comparing the growth curve here to a balance you're trying to pay down instead. Your savings figures stay entirely private, calculated locally.