Savings calculator with interest: this free tool projects balances from the deposit and interest fields on the page. Use it for goal checks before you compare products.
For pure compound growth of a lump sum, open the compound interest calculator. For future value math, use the future value calculator. Monthly investing style goals can also use the SIP calculator.
APY vs. interest rate: which number to enter
U.S. banks must state an annual percentage yield (APY) under the Truth in Savings Act (Regulation DD, 12 CFR 1030). APY already includes compounding. It is the percent your balance grows in a year with no deposits or withdrawals. The interest rate (sometimes called the nominal rate) does not include compounding.
Regulation DD defines APY as:
APY = 100 × [(1 + interest ÷ principal)365 ÷ days in term − 1]
For example, $10,000 at a 4.00% interest rate compounded daily earns about $408.08 in 365 days, so the APY is 4.08%. Two accounts with the same rate can show different APYs if they compound differently. Compare APY to APY.
This calculator compounds monthly. If you only have an APY, convert it to the equivalent monthly rate with (1 + APY)1/12 − 1. At 4.00% APY that is about 0.327% a month. Entering 4.00% as if it were a nominal monthly-compounded rate will slightly overstate growth.
Savings calculator with interest: $5,000 plus $250 a month at 4.00% APY
- Monthly rate: (1.04)1/12 − 1 ≈ 0.3274%
- Deposits: $5,000 at the start, plus $250 at the end of each month for 60 months
- Total you put in: $5,000 + $15,000 = $20,000
- Balance after 5 years: about $22,628
- Interest earned: about $2,628
As a quick check, the Rule of 72 says money doubles in about 72 ÷ 4 = 18 years at 4%. This is an approximation for estimating, not a formula banks use.
Interest is taxable, and rates change
Interest on ordinary savings accounts is taxable income in the year it is credited, and the calculator ignores tax. Most high-yield savings rates are variable, so the bank can change the APY at any time. Only a certificate of deposit locks the rate for its term. For goals more than a year away, run a second scenario at a lower rate to see how sensitive your plan is.
Keep balances inside FDIC coverage
FDIC insurance covers $250,000 per depositor, per FDIC-insured bank, per ownership category. Single accounts, joint accounts and certain retirement accounts are separate categories. If your projected balance will pass $250,000 at one bank in one category, split it across banks or ownership categories. Credit unions have similar coverage through the NCUA.
Inflation and the real return
A 4% APY grows your purchasing power only by the amount it beats inflation. If prices rise 3% over the year, the real gain is about 1%. For goals priced in future dollars, such as a home deposit or tuition, raise the target by expected inflation first, then use the savings calculator with interest to find the monthly deposit. The inflation calculator gives that future price.
Using the result for a goal
To reach a target, raise the monthly deposit before you chase a higher rate. In the example above, deposits supply almost 90% of the final balance.
Try a few what-if runs before you commit to a plan. Change the monthly deposit by $50, then change the rate by half a percentage point, and compare the final balance each time. Small, steady deposits usually matter more than a slightly higher rate, so the deposit field deserves the most attention. Also test a shorter and a longer term in the savings calculator with interest, because the number of years changes the result more than most people expect.
Last reviewed: October 2026