Project how a savings account grows from an opening deposit, optional annual and monthly contributions (each of which can rise every year), a compounding frequency, and a tax rate on interest. You get the end balance, a split of deposit versus contributions versus interest, and a year-by-year schedule.
What the results mean
| Result | What it includes |
|---|---|
| End balance | Opening deposit + all contributions + interest kept after tax |
| Initial deposit | The starting amount; shown as year 1's first deposit |
| Total contributions | Annual and monthly deposits only (not the opening amount) |
| Total interest earned | End balance minus the opening deposit minus contributions |
Examples
Default plan: $20,000 start, $5,000 a year, 3% for 10 years
An opening $20,000, a $5,000 annual contribution that grows 3% a year, and a 3% rate compounded annually reach $92,116.99. Of that, $20,000 is the initial deposit, $57,319.40 is later contributions, and $14,797.59 is interest (about 22% / 62% / 16% of the ending balance).
Same contributions, $10,000 start at 5%
Drop the opening deposit to $10,000 and raise the rate to 5%, leaving everything else the same, and the plan ends at $87,533.51 — still $57,319.40 of contributions, with $20,214.11 of interest.
Formula
Contributions are added at the end of each period. For annual compounding, interest is credited on the prior ending balance, then the year's contribution is added:
interest_year = prior balance × rate × (1 − tax)
annual deposit_year = annual contribution × (1 + increase)^(year − 1)
ending balance = prior balance + interest_year + annual deposit_year
+ 12 × this year's monthly contribution
For other compounding frequencies the same idea is applied monthly: the nominal rate is converted to an equivalent monthly rate, interest (after tax) is credited, then that month's deposit is added. The annual contribution still lands in month 12.
Saving in practice
A savings account is a deposit account that earns interest and may have minimum-balance, fee, or transaction rules set by the institution. It is more liquid than a CD, a bond, or a retirement account, and typically pays more than a checking account, which is why many people pair the two: checking for bills, savings for cash they do not need this month.
Money market deposit accounts are bank deposit accounts, distinct from money market mutual funds. They may pay a different rate or require a higher minimum balance; eligible deposits at an FDIC-insured bank receive deposit insurance within the applicable limits and ownership category. Whatever the wrapper, this calculator treats the rate you enter as a constant — real APYs change, and inflation can outpace a low savings yield, so a large idle cash balance may belong partly in higher-return options once the emergency fund is funded.
Assumptions and source
The entered rate stays constant, contributions occur on the schedule shown, and the tax field reduces every period's interest at one flat rate. Real APYs, fees, tax treatment, and deposit timing vary. Review the institution's disclosures and use the FDIC deposit-account guide to distinguish insured savings and money market deposit accounts from investment products.
Using an advertised money market APY
This savings form takes a nominal interest rate and compounding frequency. If an account advertises APY, that figure already includes compounding. Use the money market account calculator for APY-based growth, fee-waiver scenarios, and monthly account fees. Avoid entering the same APY as a nominal rate with frequent compounding.