Enter your bank's APY and how much you deposit, and see your balance year by year, the interest after tax, and what it will really buy after inflation.
Estimates for planning, not financial, tax or legal advice. Figures use US rules unless the page says otherwise.
Using the APY correctly
Banks quote savings accounts with an APY, which already includes compounding. Over a full year, a balance grows by exactly the APY, however often the bank compounds. So Calcist turns the APY into the matching rate for each deposit period, rather than dividing by 12:
i = (1 + APY)1/k − 1 k = deposits per year
At 4.5% APY with monthly deposits, i = 1.0451/12 − 1 = 0.3675% a month. Dividing 4.5% by 12 (0.375%) would overstate the growth. Deposits are added at the end of each period. The compound interest and future value calculators divide by 12, which is right for a quoted interest rate but not for an APY: for the example below they give $38,074.58 instead of $37,859.98.
Deposits happen a whole number of times. If the years don't divide evenly into deposit periods (say 2.5 years of yearly deposits), the calculator rounds to the nearest whole period and says so.
Tax and inflation
Bank interest is taxable income in the year it's paid, and your bank reports it on Form 1099-INT. Calcist takes your tax rate from each year's interest at the end of that year, as if you paid the tax out of the account. Inflation doesn't change the dollars in the account, but it shrinks what they buy:
Today's dollars = balance ÷ (1 + inflation)years
Worked example
$5,000 plus $200 a month at 4.5% APY for 10 years grows to $37,859.98: $29,000 of deposits and $8,859.98 of interest. With a 24% tax rate on the interest, it ends at $35,486.35. With 3% inflation, that's $26,405.18 in today's dollars, less than the $29,000 you deposited. After tax and inflation, this account barely keeps pace.
Limitations
- APYs on savings accounts change with the market. This assumes one rate for the whole time.
- Your real tax rate depends on your income and state. Interest in an IRA or HSA may not be taxed each year.
- Inflation varies from year to year. The Consumer Price Index from the Bureau of Labor Statistics is the usual measure.
- Investing in funds instead of a bank account? Returns are quoted per year and aren't guaranteed: use the investment calculator.
Sources
How we checked this
Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:
- $5,000 + $200 a month at 4.5% APY for 10 years = $37,859.98 ✓
- Same with 24% tax on interest = $35,486.35 ✓
- …which is $26,405.18 in today's dollars at 3% inflation ✓
- $1,000 at 5% APY for 1 year is exactly $1,050 ✓
- Same inputs at 4.5% ÷ 12 (compound interest convention): $38,074.58 ✓
- 0.01 years of yearly deposits is rounded to 1 whole deposit period, and says so ✓
- 0% APY: $5,000 + $200 a month for 10 years = $29,000 ✓
Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.
Questions people ask
How much will I have if I save $200 a month?
At 4.5% APY, $200 a month grows to about $30,095 in 10 years with no starting balance. Adding a $5,000 initial deposit brings it to $37,860.
What is the difference between APY and interest rate?
The interest rate is the rate before compounding. APY includes compounding, so it's what you actually earn in a year. A 4.4% rate compounded daily is about a 4.5% APY. Compare accounts by APY.
Is interest on a savings account taxed?
Yes, in the US it's taxed as ordinary income in the year it's credited, even if you leave it in the account. Banks send Form 1099-INT when you earn $10 or more.
What does "today's dollars" mean?
It's the future balance shrunk by inflation, so you can see what it will buy compared with prices now.
Do weekly deposits earn more than monthly?
Slightly, if the yearly total is the same, because money goes in sooner. Enter the amount per deposit, so $50 a week is about $2,600 a year.