How to use the savings interest calculator
- Type your Initial deposit and the Monthly deposit you plan to add.
- Keep APY (advertised) selected and enter the APY from your bank. If you only know the stated rate, choose APR (stated rate) and pick the Compounding frequency.
- Enter the Years, from one month up to 60 years.
- Read the Final balance, the interest earned and the year-by-year table.
How the balance is calculated
The calculator steps through every month, earning interest on the balance and then adding your deposit at month end:
balance = balance × (1 + i) + monthly deposit
i = (1 + APY)1/12 − 1 or, for an APR with n periods a year, i = (1 + APR ÷ n)n/12 − 1
APY is the yield after compounding, defined in Appendix A to Regulation DD, so twelve months at rate i add up to exactly the APY you typed.
Worked example with the default numbers
$5,000 to start, $500 a month, 4.00% APY for 20 years. The monthly rate is 1.041/12 − 1 = 0.3274%. Year 1 ends at $11,309 ($6,000 deposited, $309 interest). After 240 months the balance is $192,876: $125,000 deposited ($5,000 plus 240 × $500) and $67,876 of interest.
Limits and edge cases
- The rate is held constant. Savings rates are variable and move with the Federal Reserve, so rerun the numbers when your bank changes its APY.
- Results are before tax. Savings interest is taxable income, see IRS Topic 403. The FDIC insures deposits up to $250,000 per depositor, per bank, per ownership category.
- Saving rather than investing? The compound interest calculator suits growth with a higher assumed return. To convert a stated rate into APY, use the APY calculator, and to work out a deposit for a target, use the savings goal calculator.
Savings interest questions people ask
How much interest will $10,000 earn in a savings account at 4% APY?
$400 in the first year, for a balance of $10,400. The APY already includes compounding, so you do not compound it again. Left alone with no deposits, the $10,000 grows to $12,167 after 5 years.
What is the difference between APY and APR on a savings account?
APR is the stated yearly rate before compounding. APY is the rate you actually earn in a year once interest on interest is counted, so it is always a little higher for the same account. Banks advertise APY. Entering a 4% APY as a 4% APR compounded monthly overstates the 20-year default result by $1,624.
What is a good savings account interest rate in 2026?
In late September 2026, top online high-yield savings accounts pay roughly 4.00% to 4.50% APY, after the Federal Reserve raised its target range to 3.75% to 4.00% on September 16. The FDIC national average for savings accounts was 0.37% on September 21, so a high-yield account pays more than ten times the average.
Why is my bank balance different from the calculator?
Banks round interest to the cent, change rates as the Federal Reserve moves, and may credit interest daily or monthly on the balance at different times. This calculator holds one rate for the whole term and adds each deposit at the end of the month, so treat the result as an estimate.
Sources: CFPB, Regulation DD Appendix A; FDIC, National Rates and Rate Caps; Federal Reserve FOMC statement, September 16, 2026; IRS Topic 403; FDIC deposit insurance. Top rates: NerdWallet and Fortune savings roundups. Rates checked September 30, 2026.