This calculator works the way a savings account is quoted and paid. Enter the APY from the account page, add what you deposit each month, and read a month-by-month statement. Interest accrues daily and is credited monthly, which is how most accounts behave.
| Month | Opening | Interest | Deposit | Closing |
|---|
The table above is the statement: $10,000.00 at 4.00% APY with a $200.00 monthly deposit reaches $25,402.33 after 5 years — $22,000.00 deposited and $3,402.33 of interest. Year-end balances along the way: $12,843.69, $15,801.12, $18,876.86, $22,075.62, $25,402.33. Without the monthly deposit, the same starting balance and APY reach $12,166.53 after 5 years.
A savings account quoted in APY accrues interest daily and credits it once a month. Rather than track every single day, this calculator uses the equivalent monthly growth factor: g = (1 + APY)^(1/12). Each month the balance grows by that factor, and any deposit lands at month end.
On the default $10,000.00 at 4.00% APY with a $200.00 monthly deposit: month 1 earns $32.74 in interest and closes at $10,232.74. Month 2 earns $33.50, closing at $10,466.24, because interest is now calculated on a slightly larger balance. Month 3 earns $34.26, closing at $10,700.50.
Rate-mode check: a 4.00% nominal rate compounded daily works out to a 4.0808% APY — switch "Rate type" to "Interest rate + compounding" above to enter a rate this way instead of an APY.
Balancenext = Balance × (1 + APY)1/12 + Deposit
This applies to accounts quoted in APY with interest credited monthly.
This page takes the APY your bank actually advertises, adds a monthly deposit, and produces a statement — the way a real savings account works. The daily compound interest calculator instead takes a nominal rate and a compounding frequency, lets you compare frequencies side by side, and thinks in terms of years rather than a monthly statement.
Putting money away for a fixed term instead of adding to it every month? The CD calculator is built for money you will not touch for a fixed term.
Most savings accounts accrue interest daily and credit it monthly. The bank turns the annual rate into a daily rate, applies it to each day's balance, and adds the month's total at month end. This calculator does the same thing month by month from the APY you enter: $10,000.00 at 4.00% APY earns $32.74 in the first month, and each later month earns slightly more because the credited interest joins the balance.
Enter the APY if your bank advertises one; that is what the default mode expects. APY already includes daily compounding, so adding a compounding step on top would count it twice. If you only know the nominal rate, switch to "Interest rate + compounding": a 4.00% rate compounded daily works out to a 4.0808% APY.
At 4.00% APY, $10,000.00 earns $400.00 in twelve months with no further deposits. Add $200.00 at the end of every month and the year closes at $12,843.69, of which $443.69 is interest. The extra $43.69 comes from the deposits compounding from the month they land.
Four common reasons: interest is credited on a statement date rather than at month end, the rate changed during the period, deposits or withdrawals landed mid-month, or the account tiers its rate by balance. The calculator assumes one fixed APY, deposits at month end and no withdrawals, so read it as a close estimate, not a statement forecast.
This page is built around how a savings account is quoted and paid: APY in, monthly deposit, month-by-month statement. The daily compound interest calculator takes a nominal rate and a compounding frequency and is the better tool for comparing daily, weekly, monthly and annual compounding. Use this one for a real account; use that one for the math. Read more about the difference below, and use the daily compound interest calculator for that comparison directly.
Enter deposit, APY and term to see interest earned and value at maturity.
Interest per day on any balance, plus the total accrued over any number of days.
Calculate daily compound interest with contributions and see year-by-year growth and APY.