APY calculator, for savings accounts.

APY, the annual percentage yield, is what a savings account really pays over one year once the interest itself starts earning interest. An APY calculator turns the stated interest rate into that yield, or turns an APY back into a rate, and then shows what the money grows to. This one does three jobs: it converts between a rate and APY, it grows a savings balance month by month with deposits and fees, and it compares up to three accounts. It names no bank and claims no rate. Every number in a box is an example, so type the rate you were offered.

How to use the APY calculator

1. Pick a mode under What are you working out: Savings growth, Rate to APY or Compare.
2. Type the Starting balance. In Rate to APY it is the deposit used to show a year of interest.
3. Type the Rate (%) and say under The rate is whether it is an APY or a Stated rate. Banks usually print the APY.
4. For a stated rate, choose how often Interest is added.
5. For savings growth, add the Deposit each month and the Years. Open Fee and a goal if the account has a monthly fee or you have a target.
6. Read the cards, the chart and the table. Copy result copies a line of text, Download table (CSV) saves the table and Copy link to these numbers reopens the page with the same inputs.

APY and the stated rate

The two are linked by APY = (1 + r / n)ⁿ − 1, where r is the stated rate and n is how many times a year interest is added. Turned round, r = n × ((1 + APY)^1/n − 1). For continuous compounding the formulas are APY = e^r − 1 and r = ln(1 + APY). Here is a 4% stated rate under each choice, with the interest on 10,000 in one year:

Going the other way, a 4.5% APY needs a stated rate of 4.4098% if interest is added monthly, 4.4020% if daily, 4.4260% if quarterly and 4.5000% if yearly. The more often interest is added, the lower the stated rate can be for the same yield. This is why two accounts can show different rates and still pay the same.

Savings growth

The savings mode grows the balance by the exact APY. A year at 4% APY multiplies the balance by 1.04, so each month multiplies it by 1.04^1/12, about 1.003274. Each month the page adds the interest first, then your deposit, then takes off any fee. With 5,000 to start, 200 a month and a 4% APY, the balance after 5 years is 19,319.07. You put in 17,000 and the interest is 2,319.07. A fee of 5 a month for the same 5 years takes 300 out and leaves 18,988.17, so the interest is a little lower as well, because the fee money stopped earning. With a goal of 20,000 and no fee, the balance gets there in 63 months, or 5 years and 3 months.

Comparing accounts

Compare mode runs up to three accounts from the same start, deposit and years. The default example uses made-up rates: account A at 4.25% APY with no fee, and account B at 4.50% APY with a fee of 5 a month. With 10,000 to start and 100 a month for 5 years, A ends at 18,971.89 and B at 18,826.04. The account with the higher APY comes out 145.85 behind, because its fee costs 300 in total and the extra yield does not make it back. Without the fee, B would end at 19,161.00. A fee matters most on a small balance. Leave an account’s rate empty to leave it out.

Why a bank’s figure may differ

• The page adds interest evenly each month at the exact APY. A bank may use the daily balance, so a deposit made late in a month can earn a little less than here.
• Variable rates change. The page keeps your rate for the whole time, so treat the result as one possible path, not a promise.
• Interest is usually taxable, and the page does not take tax off. Inflation lowers what the final balance will buy.

To see growth with other compounding choices, a raise in deposits or today’s money, use the compound interest calculator. For a fixed term at a fixed rate there is the CD calculator. To see what the balance would buy later, try the inflation calculator.