Daily interest is calculated by multiplying your account balance by the annual interest rate, then dividing by 365 days
Banks calculate daily interest on savings accounts using a straightforward formula: they take your balance at the end of each day, multiply it by the annual interest rate your bank offers, then divide by 365 to get that day's interest. The result is tiny — usually a few cents or less — but it compounds, meaning tomorrow's interest is calculated on today's balance plus today's interest.
The reason banks do this daily rather than monthly or yearly is that it works in your favor. Even small deposits earn interest when ready, and interest starts earning interest right away. If you deposit $100 on Monday, by Tuesday that $100 plus the few cents of Monday's interest are both earning interest.
The actual amount you see depends on three things: how much money sits in your account, what annual rate your bank pays, and how many days the money stays there. A higher balance earns more. A higher rate earns more. More days earns more. Change any one of those, and your interest changes.
Key Takeaways
- Daily interest is calculated on your ending balance each day, so deposits start earning interest when ready.
- The formula is: (your balance × annual interest rate) ÷ 365 = that day's interest.
- Interest compounds daily, meaning you earn interest on yesterday's interest, not just on your original deposit.
- Your bank posts the accumulated daily interest to your account monthly, quarterly, or annually depending on the account.
- The interest rate your bank pays can change, so the amount you earn each day may go up or down over time.
The actual formula banks use
Here is the calculation broken into steps. Say your bank pays 4.5% annual interest and your account balance at the end of the day is $5,000.
Step 1: Convert the annual rate to a decimal. 4.5% becomes 0.045.
Step 2: Multiply your balance by that decimal. $5,000 × 0.045 = $225.
Step 3: Divide by 365 days. $225 ÷ 365 = $0.616 per day (about 62 cents).
So on that day, your account earns roughly 62 cents. Tomorrow, if your balance is still $5,000 plus the 62 cents from today, the calculation starts over with the new balance. This is compounding in action — your interest earns interest.
Banks do not pay you that 62 cents every single day. Instead, they accumulate it and deposit the total into your account on a schedule: some banks credit interest monthly, others quarterly, and some annually. Your account statement or online banking portal will show you when your bank credits interest.
Why the daily calculation matters more than you might think
Daily interest calculation is a real advantage when you move money in and out of your account. If you deposit $2,000 on the 15th of the month, that $2,000 starts earning interest that same day, not on the 1st of next month. If you withdraw $500 on the 20th, only the remaining $1,500 earns interest from the 21st onward.
This is different from how some older savings products worked — they used to calculate interest only on your lowest balance during the month, or only on balances held for a full month. Daily interest means you do not lose out for deposits that arrive mid-month or withdrawals that happen before month-end.
Over a year, this adds up. A person who deposits $100 weekly into an account earning 4% annual interest will earn more total interest than someone who deposits $5,200 all at once on January 1st, because each weekly deposit starts earning when ready. The difference is not huge, but it is real money.
How interest rates change and what that means for your earnings
The interest rate your bank pays is not fixed forever. Banks raise rates when the Federal Reserve raises its benchmark rate, and they lower rates when the Fed cuts. Your bank might also change rates independently — they might lower rates even if the Fed does not, or raise them to attract new customers.
When your rate changes, your daily interest calculation changes too. If your bank raises your rate from 4.5% to 5%, the 62 cents per day you were earning on $5,000 becomes about 68 cents per day. If the rate drops to 3%, it becomes about 41 cents per day.
Your bank will notify you before a rate change takes effect. Check your email or log into your online banking to see the new rate. Some banks show you a history of past rates, which can help you understand whether you are earning more or less than you were a year ago.
The difference between daily interest and annual percentage yield
Annual Percentage Yield (APY) is the total interest you would earn in a year if you left your money untouched and rates stayed the same. It accounts for compounding — the fact that your interest earns interest. The interest rate your bank advertises (like 4.5%) is the annual rate before compounding is factored in.
Here is why that matters: if a bank pays 4.5% annual interest with daily compounding, your actual earnings over a year will be slightly higher than 4.5% because of compounding. That slightly higher number is the APY. For a $10,000 deposit at 4.5% annual rate with daily compounding, the APY might be 4.60% — meaning you earn about $460 instead of $450.
When you compare savings accounts at different banks, look at the APY, not the annual rate. APY tells you the real amount you will earn. Banks are required to show you the APY prominently, usually right next to the annual rate.
What happens when you withdraw money mid-month
If you withdraw money before your bank credits interest, you do not lose the interest you earned up to that point. The daily interest you accumulated stays in your account. Only the balance going forward changes.
For example: your balance on the 1st is $5,000, and you earn 62 cents per day. On the 15th, you withdraw $2,000. From the 1st through the 14th, you earned interest on $5,000 (about $8.68). From the 15th onward, you earn interest only on the remaining $3,000 (about 41 cents per day). When your bank credits interest at month-end, you receive the full $8.68 plus the interest from the 15th onward.
Some older accounts had penalties for withdrawals or required you to maintain a minimum balance to earn any interest at all. Most modern savings accounts do not. You can withdraw whenever you want without losing the interest you have already earned.
How to track your interest earnings
Your bank shows you interest earned in two places: your monthly or quarterly statement, and your online banking portal. The statement lists the total interest posted that period. The portal usually shows a running total of interest earned year-to-date.
If you want to estimate what you will earn in a month, use the daily formula. Multiply your average balance by the annual rate, divide by 365, then multiply by the number of days in the month. If your balance fluctuates a lot, use your lowest balance to get a conservative estimate, or your highest balance to see the best-case scenario.
Some banks also send you an interest statement at year-end showing total interest earned. This is useful for tax purposes if you earned more than $10 in interest — you may need to report it on your tax return. Your bank will send you a Form 1099-INT if you earned $10 or more in interest during the year.
Frequently Asked Questions
Does my bank calculate interest on weekends and holidays?
Yes. Banks calculate daily interest on all 365 days of the year, including weekends and holidays. The formula divides by 365, not by 260 business days. Your money earns interest every single day it sits in the account.
What if my bank uses 360 days instead of 365?
Some banks use 360 days in their calculation, which is slightly more favorable to the bank and slightly less favorable to you. This is rare in consumer savings accounts but more common in other financial products. Check your account disclosure or ask your bank directly which method they use.
Can I earn interest on interest before my bank credits it to my account?
Yes. Even though your bank does not deposit the interest into your account until monthly or quarterly, the interest you earned yesterday is part of your balance today, so it earns interest. This is compounding. The more frequently your bank compounds (daily is the most frequent), the more you earn.
If I move money between my savings and checking account, does it affect my interest?
Only the balance in your savings account earns interest. Money in checking typically earns little to no interest. When you transfer money out of savings, that amount stops earning interest when ready. When you transfer money in, it starts earning interest that day.
Why do I earn less interest than the APY suggests?
The APY assumes your balance stays the same all year. If you withdraw money, your balance is lower, so you earn less. If you deposit money partway through the year, you earn less than the full APY because the money was not there for the whole year. The APY is a best-case scenario, not a may provide.