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Daily Interest Calculator
See how much interest builds up each day on a savings balance or loan, using simple or daily compounding. Enter your numbers and press Calculate.
Written by TopicDrill Editorial Team·Updated June 2026
Interest accrued over time
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How daily interest works
The daily interest rate is simply the annual rate split across the year. Divide the annual rate by 365 and you get the fraction earned or charged each day. Multiply that by your balance and you have one day of interest. Add up every day in the period and you get the total, which the chart above traces as it climbs.
The accrual method matters. Simple daily interest always uses the starting principal, so the line is straight. Daily compounding folds each day's interest into the balance, so the curve bends upward as interest starts to earn interest of its own.
A quick example
Hold $10,000 at 5% a year. The daily rate is about 0.0137%, so the first day earns roughly $1.37. Over 365 days with daily compounding the balance grows by about $513, a touch more than the $500 you would get from simple interest, because of compounding.
Things to keep in mind
Results are estimates. Real accounts may use a 360-day convention, round differently or apply fees, and rates can change. For everyday guidance on interest and saving, the Consumer Financial Protection Bureau is a reliable source. To project longer horizons, try our compound interest calculator.
Frequently asked questions
How is daily interest calculated?
Start with the daily rate, which is the annual rate divided by 365. Multiply it by the balance to get one day of interest. With simple accrual the rate always applies to the original principal. With daily compounding, each day's interest is added to the balance, so the next day's interest is slightly larger.
What is the difference between simple and compound daily interest?
Simple daily interest is figured on the original principal every day, so it grows in a straight line. Daily compounding adds each day's interest back to the balance, so interest then earns interest. Over short periods the two are close, but compounding pulls ahead the longer you wait.
Why do savings accounts and cards use daily interest?
Many savings accounts accrue interest daily and pay it monthly, while credit cards often charge interest on a daily balance. Calculating per day lets the rate reflect exactly how many days your money was deposited or borrowed, which is fairer than a flat monthly figure.
Does the number of days in a year matter?
Yes. This calculator divides the annual rate by 365. Some institutions use 360 days, which slightly raises the daily rate. Check your account terms if you need to match a statement exactly, since the convention affects the result.
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