Direct answer
APY, or annual percentage yield, is the total amount you earn on savings in one year after compounding is included. An interest rate, on its own, is the base rate applied to your original balance. It does not include interest earned on earlier interest.
That is the whole difference in one sentence. If an account pays interest once a year, APY and the interest rate are the same. If an account adds interest monthly or daily, APY is slightly higher, because each interest payment starts earning interest of its own. APY is therefore the fairer number for comparing savings accounts, because it shows the full one year result, not just the starting rate.
This post is educational only. It is not financial advice, and it does not recommend any bank, account, or product.
What is an interest rate?
An interest rate is a percentage used to calculate interest. For savings, it tells the bank how much to pay you for keeping money in the account. For borrowing, it tells you how much you pay for using someone else’s money.
Suppose you deposit 2,000 in an account with a 4 percent annual interest rate, and interest is paid only once at the end of the year. You earn 4 percent of 2,000, which is 80. Your balance becomes 2,080.
The interest rate alone, however, does not tell you when interest is added. That timing matters. If interest is added during the year, your balance grows during the year, and later interest is calculated on a larger balance. The interest rate by itself does not show that extra growth. APY does.
An interest rate is also used for loans, credit cards, and mortgages. In that case, it is a cost, not a reward. Always check whether the rate applies to saving or to borrowing.
What is APY?
APY stands for annual percentage yield. It is the effective annual return on a deposit account after compounding. Compounding means interest is added to your balance, and then future interest is earned on both your original deposit and the interest already added.
In plain terms, APY answers this question: if I leave my money alone for one full year, and I do not add or withdraw anything, what percentage will I have earned by the end of the year?
Banks in the United States are required to disclose APY for deposit accounts, so savers can compare accounts on the same basis.
APY assumes you leave the money for the full year, with no deposits or withdrawals. If you withdraw money during the year, or if the rate changes, your actual earnings will differ. A variable APY can rise or fall during the year, and the advertised APY at account opening is not a promise for the whole year. Always check whether the APY is fixed or variable, and whether it applies to your full balance or only to part of it.
Our guide to whether a high yield savings account is safe explains why a high APY alone is not enough reason to choose an account. Safety, access, fees, and terms matter too.
How compounding makes APY different
Compounding is interest earning interest. It is a small effect in one year, and a larger effect over many years, because the base keeps growing.
Think of it in steps. In month one, the bank calculates interest on your original deposit. That interest is added to your balance. In month two, the bank calculates interest on your original deposit plus the month one interest. The balance is slightly larger, so the interest is slightly larger. The same step repeats each month.
The standard formula is APY equals (1 plus r divided by n) to the power of n, minus 1. Here, r is the nominal annual interest rate as a decimal, and n is the number of compounding periods in a year. For monthly compounding, n is 12. For daily compounding, n is 365. For annual compounding, n is 1.
You do not need to memorise the formula to use APY well. More frequent compounding gives a slightly higher APY for the same nominal rate, because interest starts earning interest sooner.
That difference is usually small in one year. At a 4 percent nominal rate, annual compounding gives an APY of 4.00 percent, monthly compounding about 4.07 percent, and daily compounding about 4.08 percent. Do not choose an account mainly for daily rather than monthly compounding.
Over longer periods, the effect grows, because each year starts from a larger balance. That is why compounding matters more for long term savings, such as an emergency fund you keep for years.
A worked example: one deposit, three compounding schedules
The following numbers are an example only, not a forecast and not a recommendation. They show how the maths works, so you can follow the idea with your own numbers.
Suppose you deposit 2,000 and leave it alone for one year. The nominal annual interest rate is 4 percent in all three cases. Only the compounding schedule changes.
First, annual compounding. Interest is calculated once, at the end of the year. You earn 4 percent of 2,000, which is 80. Your balance becomes 2,080. The APY is 4.00 percent.
Second, monthly compounding. The monthly rate is 4 percent divided by 12, which is about 0.3333 percent per month. Each month, interest is added, and the next month interest is calculated on the new balance. After 12 months, the APY is about 4.07 percent. You earn about 81.48, and your balance becomes 2,081.48. That is 1.48 more than annual compounding, purely from monthly compounding.
Third, daily compounding. Interest is calculated on 365 days. The APY is about 4.08 percent. You earn about 81.62, and your balance becomes 2,081.62. That is only 0.14 more than monthly compounding. Daily compounding is slightly better, but the difference is very small on a 2,000 balance.
Now look at a longer period, still as an example only. If you left the same 2,000 for five years at 4 percent compounded monthly, with no deposits, withdrawals, or rate change, your balance would be about 2,441.99. In real life, rates change, fees apply, and taxes may apply, so a real result will differ.
The lesson is simple. APY already includes the compounding schedule, so you do not need to work it out yourself when you compare accounts. Compare APY to APY, for the same type of account, and then check the other terms.
APY vs APR in plain terms
APY and APR sound alike, and they are easy to confuse, but they describe opposite sides of money.
APY is for saving. It shows how much a deposit account can earn in one year, including compounding. A higher APY, all else equal, means more earnings for a saver.
APR stands for annual percentage rate. It is for borrowing. It shows the annual cost of a loan or credit product, including the interest rate and, in many cases, certain fees. A lower APR, all else equal, means lower borrowing cost.
Do not compare a savings APY with a loan APR as if they were the same measure. A savings account with a 4 percent APY and a credit card with a 20 percent APR are not two versions of the same number. One is what you earn, and the other is what you pay. Mixing them up can lead to a bad decision, such as thinking a loan is cheap because its number looks close to a savings number.
Some investment or rewards products quote an APR when they mean an estimated annual return, without compounding included. Always check what the number includes, whether it is earnings or cost, and whether compounding is included.
How to compare savings accounts fairly
Start with APY, not with the headline interest rate. If two savings accounts have the same APY, they should earn the same amount in one year on the same balance, assuming no deposits, withdrawals, fees, or rate changes. If one APY is higher, it should earn more, all else equal.
Then check five other things before you choose.
First, is the APY fixed or variable? Most savings APYs are variable, which means the bank can change them when market rates change. A high APY today can fall next month. That does not make the account bad, but it means you should not plan as if the current APY is locked in.
Second, does the APY apply to your full balance? Some accounts pay a higher APY only up to a balance limit, and a lower APY above that limit. Others pay a lower APY unless you meet a minimum balance or a monthly condition. Read the balance tiers and conditions, not just the headline number.
Third, what are the fees? A monthly maintenance fee, an excess withdrawal fee, or a minimum balance penalty can erase the extra interest from a slightly higher APY. Work out the net result: interest earned, minus fees paid. A slightly lower APY with no fee can beat a slightly higher APY with a monthly fee on a small balance.
Fourth, how easy is it to get your money? A savings account should be easy to access in an emergency, with a clear transfer time. If withdrawals are slow, limited, or costly, that cost matters, even if the APY looks attractive. Our guide to how much to keep in an emergency fund explains why access matters as much as return for emergency money. Our guide to how to build an emergency fund from zero is a good place to start if you do not have one yet.
Fifth, is the account covered by deposit insurance, and up to what limit? In the United States, that usually means FDIC insurance for banks or NCUA insurance for credit unions, up to the published limit per depositor and ownership category. In other countries, the scheme and limit differ, so check the rules where you live. Our guide to the difference between a checking and a savings account and our guide to a high yield account versus a normal savings account can help you place APY in context, because a checking account is for everyday spending, while a savings account is for money you want to keep separate and let grow.
Use a simple checklist. Write down APY, fixed or variable, balance tiers, monthly fee, withdrawal rules, and insurance cover, side by side. The best account is rarely the one with the highest number alone.
Common mistakes to avoid
Do not compare an interest rate with an APY as if they were equal. The interest rate is the starting rate. APY is the one year result after compounding. If you compare a 4 percent interest rate on one account with a 4.07 percent APY on another, you may think the second account is better by 0.07 percent, when in fact both could be the same account described two ways. Compare APY to APY.
Do not assume APY includes fees. APY shows interest growth only. It does not subtract monthly fees, transfer fees, or penalties. Always check fees separately.
Do not assume a high APY will last. Variable APYs move with market rates and bank policy. If you build a plan that only works at the current APY, a rate fall can break it. Keep a buffer, and review the rate from time to time.
Do not chase a small APY gap and ignore access. Moving an emergency fund to a slightly higher APY account that is hard to access, or that charges for withdrawals, can cost more in a real emergency than the extra interest is worth.
Do not forget that APY assumes a full year with no change. If you deposit, withdraw, or add money during the year, your actual earnings will differ. APY is a comparison tool, not a promise about your personal result.
Do not confuse APY with total return on investments. APY is for deposit accounts, where the return is interest. Stocks, bonds, and funds do not have an APY in the same sense, because their returns vary and can fall.
Frequently asked questions
Is APY always higher than the interest rate?
APY is equal to or higher than the nominal interest rate. It is equal when interest is paid only once a year. It is higher when interest is added more often during the year, because interest earns interest. It is never lower than the nominal rate for a standard deposit account, assuming no fees are included in the calculation.
Can I earn the full APY if I withdraw money during the year?
Not necessarily. APY assumes you leave the full balance for one year, with a steady rate. If you withdraw money, future interest is calculated on a smaller balance.
Does a higher APY always mean a better account?
No. A higher APY is attractive, but fees, balance tiers, withdrawal rules, access speed, and whether the rate is fixed or variable can change the real result. Compare the full terms, not just the headline APY.
What is the difference between APY and APR?
APY is for saving. It shows annual earnings including compounding. APR is for borrowing. It shows annual borrowing cost, often including certain fees. Higher APY is generally better for a saver. Lower APR is generally better for a borrower.
Why did my savings APY change?
Most savings APYs are variable. When central bank rates change, or a bank changes its pricing, savings APYs often move too.
Should I move my money for a small APY difference?
It depends on the size of the difference, your balance, fees, and effort. On a small balance, a 0.10 percent APY gap earns only a few dollars in a year. Before you move money, work out the extra interest in dollars, minus any fees or transfer delays.
Conclusion, and your first step this week
An interest rate is the starting rate. APY is the full one year result after compounding. That is why APY is the fairer number for comparing savings accounts, and why two accounts with the same interest rate can still have different APYs.
Start this week with three actions. First, find the APY on your current savings account, and check whether it is fixed or variable, and whether it applies to your full balance. Second, write down any monthly fee and withdrawal rules, so you can see the net result, not just the headline rate. Third, compare APY to APY for similar accounts, side by side, using the checklist in this post, before you decide whether a change is worth it.
This post is educational only. It is not financial advice, and it does not recommend any bank or account.