Daily Compound Interest Calculator
Calculate compound daily interest over an exact number of days. Select a 360, 365, or 366-day convention and compare the result with simple and continuous interest.
Written and checked by TheToolNet Editorial Team · Last reviewed: September 27, 2026 · Editorial method
Balance = principal × (1 + annual rate ÷ day-count basis)number of days.
Compound interest daily
Daily compounding versus daily accrual
Interest can accrue every day without necessarily being added to principal every day. Compounding means credited interest itself begins earning interest. Check the contract or account disclosure for the actual crediting and day-count method.
360, 365, and 366-day bases
A 365-day basis divides the quoted annual rate by 365. A 366-day basis can be relevant to leap-year calculations. Some products use a 360-day denominator. Choosing a smaller denominator produces a larger daily periodic rate for the same nominal annual rate.
Compare simple and continuous interest
The result includes simple interest over the same fraction of a year and the mathematical continuous-compounding limit. These are comparisons, not claims about how a particular institution calculates interest. For non-compounding daily interest, use the simple interest calculator by days.
Frequently asked questions
Does daily compounding mean 365 periods every year?
Often, but not always. Product terms can use different conventions, leap-year rules, or posting schedules.
Can I calculate a negative return?
Yes, above −100% annually. It is a mathematical scenario and may not represent a real account.