Interest accrues daily and compounds, usually monthly or daily
A high-yield savings account (HYSA) earns interest on the money you deposit. The bank calculates how much interest you owe you based on your balance and the annual percentage yield (APY) it advertises. That interest gets added to your account on a schedule — most often monthly, though some accounts compound daily.
The key difference between a HYSA and a regular savings account is the rate. A traditional savings account might pay 0.01% APY. A HYSA typically pays between 4% and 5.35% APY, depending on the bank and the current interest rate environment. The higher the APY, the more interest you earn on the same balance.
Interest compounds, meaning you earn interest on the interest that was already added to your account. If you deposit $10,000 and earn $500 in interest over a year, that $500 becomes part of your balance. The next month, the bank calculates interest on $10,500, not just the original $10,000. Over time, this compounding effect makes your money grow faster than simple interest would.
Key Takeaways
- Interest in a HYSA is calculated daily based on your balance but usually added to your account once a month.
- The APY listed by the bank is the rate you earn over a full year if your balance stays the same and interest compounds.
- Compounding means you earn interest on previously earned interest, which accelerates growth over time.
- The exact amount you earn depends on your balance, the APY, and how long your money stays in the account.
- Interest rates on HYSAs change over time and are set by the bank, not locked in for a year.
How the bank calculates your daily interest
Banks use a formula to calculate interest each day. They take your account balance, multiply it by the APY, and divide by 365 (or 366 in a leap year). That gives them the interest earned for one day. They repeat this calculation every single day, using your current balance — which changes each time you deposit or withdraw money.
For example: if your HYSA has a $10,000 balance and the APY is 5%, the daily interest is roughly $1.37 per day ($10,000 × 0.05 ÷ 365). If you deposit another $5,000 the next day, the daily interest jumps to about $2.05 per day ($15,000 × 0.05 ÷ 365). If you withdraw $3,000, it drops to about $1.64 per day ($12,000 × 0.05 ÷ 365).
The bank keeps a running total of all the daily interest earned throughout the month. At the end of the month (or on the date the bank specifies), it deposits that total into your account. That lump sum becomes part of your balance, so next month's interest calculations include it.
Why your interest payment changes month to month
Even if the APY stays the same, the interest you receive each month will vary because your balance changes. Deposits increase the interest you earn that month. Withdrawals decrease it. A month where you deposit $5,000 halfway through will earn more interest than a month where you withdraw $5,000 halfway through.
The APY itself also changes. Banks adjust the rates they offer based on what the Federal Reserve does with interest rates. When the Fed raises rates, banks often raise HYSA rates within days or weeks. When the Fed cuts rates, banks usually cut HYSA rates as well. You might see your APY drop from 5.35% to 5.10% with no warning, and your monthly interest payment will shrink accordingly.
Some banks may provide a rate for a set period — for example, "5.35% APY for 3 months" — but most HYSAs have variable rates that can change at any time. Check your account statements or log into your bank's website to see what rate you are currently earning.
The difference between daily and monthly compounding
Most HYSAs compound interest daily, meaning the bank adds interest to your account every single day. A few compound monthly. The difference is small but real over long periods.
With daily compounding, the interest you earn on day one gets added to your balance on day one (or at the end of the month, but it counts toward your balance for the rest of the month). That means day two's interest calculation includes the day one interest. With monthly compounding, all the daily interest sits in a holding area until the end of the month, then gets added all at once.
Over a year, daily compounding typically earns you slightly more than monthly compounding — usually a difference of less than $10 on a $10,000 balance. It matters more the longer your money stays in the account and the higher the APY. When comparing HYSAs, daily compounding is a small advantage, but the APY itself matters far more.
What happens to interest if you withdraw money
Interest you have already earned stays in your account. If you withdraw $5,000 and the bank has already added that month's interest, the interest remains. You only lose the interest you would have earned on the $5,000 going forward.
Some banks calculate interest through the end of the month even if you withdraw mid-month. Others stop calculating interest the moment you withdraw. Read your account agreement or call the bank to confirm. The difference is usually just a few dollars, but it matters if you are planning a large withdrawal.
HYSAs have no penalty for withdrawals, unlike certificates of deposit (CDs). You can take money out whenever you want without losing interest you have already earned. Federal rules used to limit you to six withdrawals per month, but that rule was suspended in 2020 and has not returned.
How to estimate what you will earn
You can calculate roughly how much interest you will earn using a simple formula: (Balance × APY) ÷ 12 = Monthly Interest. This assumes your balance stays the same all month and the APY does not change.
For a $25,000 balance at 5% APY: ($25,000 × 0.05) ÷ 12 = $104.17 per month. Over a year, that would be about $1,250 in interest (though the actual amount will be slightly higher because of compounding).
For a more precise estimate, use an online HYSA calculator. Enter your balance, the APY, and how long you plan to keep the money. The calculator will show you the effect of daily compounding. Keep in mind that if the APY changes during that time, your actual earnings will differ from the estimate.
Why HYSA interest rates are not may provide
Banks set their own rates and change them whenever they want. There is no contract saying your rate will stay at 5.35% for a year. The rate is variable, which means it can go up or down based on market conditions and the bank's business decisions.
When the Federal Reserve raises its benchmark interest rate, banks usually raise HYSA rates within a few days because they can attract more deposits by offering higher rates. When the Fed cuts rates, banks cut HYSA rates because they do not need to offer as much to keep deposits. This happens automatically — you do not have to do anything.
If you want a may provide rate, you would need a CD (certificate of deposit), which locks in a rate for a set term. But CDs have withdrawal penalties if you take the money out early, and they typically pay less than HYSAs. Most people choose HYSAs for the combination of high rates, daily access, and no penalties.
Frequently Asked Questions
Do I have to pay taxes on HYSA interest?
Yes. Interest earned in a HYSA is taxable income. At the end of the year, the bank sends you a 1099-INT form showing how much interest you earned. You report that amount on your tax return. The interest is taxed at your ordinary income tax rate, not as a capital gain.
What if I deposit money mid-month — do I earn interest on it right away?
Yes. The bank calculates interest daily based on your current balance. Money you deposit on day 15 of the month starts earning interest on day 15. You will receive interest on that deposit when the bank compounds interest at the end of the month (or daily, depending on the account).
Can the bank lower my interest rate without telling me?
Yes. Banks can change variable rates at any time without advance notice, though most send an email or notification when rates change. Check your account regularly or set up alerts through your bank's app to track rate changes. If the rate drops significantly, you can move your money to a different HYSA.
Is the APY the same as the interest rate?
Not exactly. The interest rate is the percentage the bank pays. The APY (annual percentage yield) includes the effect of compounding. If a bank compounds daily, the APY will be slightly higher than the stated interest rate. Most banks advertise the APY because it is the more accurate number for what you will actually earn.
What happens to my interest if the bank fails?
Your deposits and all earned interest are protected by the FDIC (Federal Deposit Insurance Corporation) up to $250,000 per account holder per bank. Interest that has been added to your account counts toward that limit. If the bank fails, the FDIC pays you the full amount, including interest earned through the date of failure.