Compound Interest Calculator
See how daily, monthly, quarterly and annual compounding change the same deposit held at the same nominal rate.
The honest answer about compounding frequency
No feature in banking is more over-marketed than compounding frequency. Daily against monthly on $25,000 at 4.50% across five years is worth roughly $15 — in total, not per year. Those same five years at a rate just 0.10% higher are worth about $140. Chase the rate, and treat the compounding schedule as a tiebreaker between otherwise identical offers.
Frequency genuinely counts on long horizons and large balances. On $250,000 across 20 years, daily against annual compounding at 4.5% comes to a difference of several thousand dollars. The switcher above lets you check your own numbers instead of taking either cliché on faith.
The rule of 72, checked against real math
The old shortcut holds that money doubles in 72 ÷ rate years — so 16 years at 4.5%. Run this calculator’s formula and the exact answer is 15.7 years. At savings-account rates the rule is slightly pessimistic and perfectly good for dinner-table planning, but the point of publishing the formula is that you never have to settle for “good enough”: drag the term slider to your actual horizon and read the actual number.