Savings Interest Calculator
Enter your starting balance, your account's APY, and what you add each month to see where the balance ends up — and how much of it is interest rather than your own deposits. Works for high-yield savings accounts, money market accounts, or any account quoted in APY.
| Projected balance | $0 |
| Total you deposited | $0 |
| Interest earned | $0 |
Assumes a constant APY, monthly compounding, and deposits at the end of each month. Interest is shown pre-tax. Estimates only, not financial advice.
About this estimate
APY is the effective annual yield, so the calculator derives the monthly rate that compounds back to exactly your APY over twelve months and applies it month by month, crediting your deposit after each month's interest. With no deposits, a balance grows by precisely the APY each year — that is the definition of APY, and it is what makes this projection bank-agnostic even though banks compound on different schedules.
Two simplifications matter for long horizons. The rate is held constant, while real savings rates float with the broader interest-rate environment — a five-year projection at today's APY is a scenario, not a forecast. And the result is pre-tax: interest is ordinary income each year, so your after-tax growth depends on your marginal rate (our marginal vs. effective guide explains how to find it). The math itself is covered by the site's automated test suite against hand-computed values.
Frequently asked questions
What is the difference between APY and APR?
APY (annual percentage yield) includes the effect of compounding: it is the total percentage your balance actually grows in a year. APR is the simple rate before compounding. Banks advertise savings accounts in APY, which is why this calculator asks for APY — no compounding adjustment is needed on your part.
How often is savings interest compounded?
It varies by bank — daily and monthly are both common. Because APY already reflects compounding, the annual result is the same either way; only the within-year path differs slightly. This calculator compounds monthly, which matches how most people deposit.
Is savings account interest taxable?
Yes. Interest is ordinary income, taxed at your marginal rate in the year you earn it, whether or not you withdraw it. Banks report it on Form 1099-INT (generally issued when interest is $10 or more). The projection here is pre-tax.
Will the APY stay the same for my whole projection?
Probably not. Savings rates are variable: banks move them with the interest-rate environment, and the APY you sign up at is not locked. Treat long projections as a scenario at a constant rate, and re-run the numbers when your bank changes its rate.
Saving for retirement instead? The 401(k) growth calculator handles employer matches and contribution limits.