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.
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.
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.
Saving in practice
A savings account is a deposit account that earns interest, usually with a withdrawal limit and sometimes a minimum balance. 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 accounts work like savings but often yield a little more because the bank invests the deposits; they can also come with debit-card access and market-linked risk. 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.