Interest Per Day Calculator
Find out how much interest builds up per day on a balance, based on the principal amount and annual interest rate.
What This Calculator Does
This calculator shows how much simple interest accrues on a balance per day, which is useful for understanding credit card debt, short-term loans, or how quickly interest builds on savings.
The Method
Daily interest is calculated as: Principal × (Annual Rate ÷ 100) ÷ Days in Year. Most lenders use a 365-day year, though some commercial loans use a 360-day ‘banker’s year,’ which slightly increases the daily rate. Weekly, monthly, and yearly figures are simple multiples of the daily amount, assuming the balance stays constant.
Note: Real-world balances change daily as payments and new charges are applied, and many accounts compound interest rather than accruing it as flat simple interest. This calculator gives a straightforward daily-rate estimate on a fixed balance, not a full amortization schedule.
This tool is for general educational purposes only and is not financial advice.