How Savings Account Interest Is Calculated (Daily Compounding)
Ever wondered how savings interest is calculated? Most U.S. savings accounts calculate interest every day on your balance and add it to the account once a month. This guide shows the exact steps with a $10,000 example.
Quick answer
Most banks use a daily rate (the yearly rate ÷ 365) on your daily balance, then credit the total once a month. At 4% compounded daily, $10,000 earns about $1.10 a day and about $32.93 over 30 days.
How savings interest is calculated, step by step
- Daily rate: the yearly interest rate ÷ 365. At 4%, that is about 0.011% a day.
- Daily interest: balance × daily rate. $10,000 × 0.04 ÷ 365 ≈ $1.10.
- Compounding: each day the interest is added to the amount that earns interest the next day.
- Crediting: the bank adds the month’s interest to your account, usually at the end of the statement cycle.
Daily balance vs average daily balance
Banks must tell you which method they use. With the daily balance method, interest is calculated on each day’s actual balance. With the average daily balance method, the bank averages your balance over the period and applies the rate to that average. For a steady balance, both give about the same result.
Example: $10,000 for one month
| APY | Interest in the first month |
|---|---|
| 0.5% | $4.16 |
| 2% | $16.52 |
| 4% | $32.74 |
| 5% | $40.74 |
Because interest compounds, the second month earns slightly more than the first, and so on. The APY shows the full-year result including that effect.
What this means for you
- Compare accounts by APY; it already includes daily compounding.
- Interest is usually credited monthly; closing an account mid-cycle can forfeit some interest at some banks.
- Your savings rate can change; check it a few times a year.
Frequently asked questions
How is interest calculated on a savings account?
Usually daily on your balance, using the yearly rate divided by 365, and credited monthly.
Do savings accounts compound daily?
Many do, though some compound monthly. The account disclosure explains it, and the APY includes the effect.
How much interest will I earn per day?
Balance × rate ÷ 365. $10,000 at 4% earns about $1.10 a day.
Why did I earn less interest this month?
Months have different numbers of days, your balance may have changed, or the bank may have lowered its rate.
Is savings interest taxable?
Yes, in most cases it is taxable income. See is interest on savings taxable.
Related guides and calculators
- Daily vs monthly vs annual compounding
- APY calculator
- How much interest will $10,000 earn?
- High-yield savings account calculator
Sources
- FDIC: National rates and rate caps
- Consumer Financial Protection Bureau (CFPB)
- MonetaryReports: How we calculate
This guide is for educational purposes only and is not financial advice. The figures are estimates before taxes, fees and inflation, and real rates, returns and rules change over time.
