Daily interest calculator

Your payment, your payoff plan. Free, no ads, no signup.

Daily & monthly interest

What your balance costs per day and per month, and the prepaid (per-diem) interest due at closing.

Created for Phil Stevenson, Mortgage Nerd®, NMLS 365768. Calculation methods and limitations.

Estimate interest by the day

Daily interest equals principal × annual rate ÷ day-count basis. At $400,000 and 6.5%, a 365-day basis gives $71.23 per day, or $783.56 for 11 days. A 360-day basis gives $72.22 per day.

Match your lender’s convention

Confirm the day-count basis and number of chargeable days on your Loan Estimate or Closing Disclosure. Actual/360 and 30/360 conventions are different; this tool multiplies the daily amount by the days you enter. It does not determine which closing dates are chargeable.