Quick answer
A savings calculator projects what a starting balance plus regular deposits grows to at a given APY. Deposit $10,000, add $300 a month at 4.5% APY, and after 10 years you hold about $61,029 — $46,000 of deposits and roughly $15,029 of interest, earned month by month as each balance compounds.
How the Savings Calculator works, step by step
Enter your starting balance, monthly deposit, APY and years. The calculator credits interest on the balance each month, then adds your deposit, so every deposit starts earning the month after it lands. APY is the rate you actually earn over a year once compounding is included, which is why the tool asks for APY rather than the nominal rate your bank may advertise alongside it.
Read the split between deposits and interest, not just the final balance. If deposits dominate, a higher rate matters less than a higher deposit; if interest is a large share, the rate is doing real work and shopping for a better APY pays off. The year-by-year chart shows the bend: growth starts almost flat, then curves upward as interest earns interest on a larger base.
The rate you enter is a snapshot, not a promise. High-yield savings rates move with the federal funds rate, which the Federal Reserve held at 3.75% to 4.00% in October 2026 after raising it in September. Top accounts paid about 4.2% to 4.4% APY in November 2026, while the national average savings rate sat at 0.38% — the gap between those two numbers is what switching banks is worth.
The projection is pre-tax. Interest in a regular savings account is taxed as ordinary income in the year it is credited, and your bank reports it on Form 1099-INT when it exceeds $10. At a 22% marginal rate, roughly a fifth of the interest in the example below goes to tax. The calculator does not deduct tax, so treat its interest figure as the amount before the IRS takes its share.
Two assumptions deserve a second look. The calculator holds your rate and deposit constant for the whole horizon, and it assumes no withdrawals — real savings plans change both. It also shows nominal dollars: at 3% inflation, the purchasing power of the final balance is roughly three-quarters of the headline figure after 10 years. Re-run the numbers when your rate changes rather than trusting a projection made years earlier.
The formula
Future value = P × (1 + r/12)^(12t) + PMT × [((1 + r/12)^(12t) − 1) / (r/12)], where P is the starting balance, PMT the monthly deposit, r the annual rate as a decimal and t the years.
Worked example — try it on the calculator above
Worked example: $10,000 plus $300 a month for 10 years
Start with $10,000 and deposit $300 a month into an account paying 4.5% APY, compounded monthly, for 10 years. Your deposits total $46,000 ($10,000 plus 120 deposits of $300). The end balance is $61,029, so interest contributes about $15,029 — roughly a quarter of the final amount, earned without any extra deposits. Run the same plan at the 0.38% national average rate and the balance reaches only $47,074, with barely $1,074 of interest: the rate choice alone is worth about $13,955 over the decade. The interest share also grows with time: the account earns about $540 of interest in its first year, but roughly $2,600 in its tenth, because the balance doing the earning is far larger by then.
Frequently Asked Questions
What APY should I enter?
Use the APY your bank quotes, not the nominal interest rate. APY already includes compounding, so a 4.5% APY account grows slightly faster than a 4.5% nominal rate compounded monthly. In November 2026 top online accounts paid roughly 4.2% to 4.4% APY while the national average sat at 0.38%; rates are variable and move with the Federal Reserve rate.
Is the interest on savings taxed?
Yes. Interest earned in a regular savings account is taxed as ordinary income in the year it is credited, and your bank reports it on Form 1099-INT if it exceeds $10. The calculator shows pre-tax growth, so at a 22% marginal rate you would keep about 78% of the interest shown.
How much faster does monthly compounding grow money than annual?
By a small amount. At a 4.5% nominal rate, monthly compounding turns the rate into a 4.59% effective yield. Compounding frequency matters far less than the rate itself and the size of your deposits, so chase the rate first and treat frequency as a tiebreaker.
Does this calculator account for inflation?
No. It shows nominal dollars. At 3% inflation, the $61,029 balance in the worked example buys what about $45,400 buys today, so a balance growing at 4.5% gains roughly 1.5% a year in real terms before tax. Use the inflation calculator alongside this one for the real picture.
Estimates, not advice. This calculator provides educational estimates based on the inputs you enter and the assumptions shown on this page. It is not financial, tax or investment advice, and it cannot see your full situation. Verify important figures against official sources, and consider a qualified professional for decisions about your own money. See our Disclaimer and Methodology.