Grow
Compound interest calculator
See how a starting balance and a monthly deposit grow when the same annual rate is compounded every month. This is a savings path, not a loan payment.
Results
- Future value
- $144,572.72
- Contributed by you
- $58,000.00
- Interest earned
- $86,572.72
- Year 1$13,201.42
- Year 6$33,033.24
- Year 11$61,147.34
- Year 15$91,881.93
- Year 20$144,572.72
| Year | Contributed | Interest | Balance |
|---|---|---|---|
| 1 | $12,400.00 | $801.42 | $13,201.42 |
| 2 | $14,800.00 | $1,834.27 | $16,634.27 |
| 3 | $17,200.00 | $3,115.28 | $20,315.28 |
| 4 | $19,600.00 | $4,662.39 | $24,262.39 |
| 5 | $22,000.00 | $6,494.83 | $28,494.83 |
| 6 | $24,400.00 | $8,633.24 | $33,033.24 |
| 7 | $26,800.00 | $11,099.74 | $37,899.74 |
| 8 | $29,200.00 | $13,918.03 | $43,118.03 |
| 9 | $31,600.00 | $17,113.55 | $48,713.55 |
| 10 | $34,000.00 | $20,713.58 | $54,713.58 |
| 11 | $36,400.00 | $24,747.34 | $61,147.34 |
| 12 | $38,800.00 | $29,246.20 | $68,046.20 |
| 13 | $41,200.00 | $34,243.79 | $75,443.79 |
| 14 | $43,600.00 | $39,776.14 | $83,376.14 |
| 15 | $46,000.00 | $45,881.93 | $91,881.93 |
| 16 | $48,400.00 | $52,602.60 | $101,002.60 |
| 17 | $50,800.00 | $59,982.60 | $110,782.60 |
| 18 | $53,200.00 | $68,069.60 | $121,269.60 |
| 19 | $55,600.00 | $76,914.70 | $132,514.70 |
| 20 | $58,000.00 | $86,572.72 | $144,572.72 |
How to use this page
- Replace the sample numbers with your own. Nothing is sent to a server.
- Read the result. It changes as you type.
- Open the formula if you want to recompute the result by hand.
- Copy the result if you want to keep it. The numbers you type stay in this browser and are not added to the address.
Formula
Monthly rate r = annual rate ÷ 100 ÷ 12. After n months, balance = principal × (1+r)^n + deposit × [((1+r)^n − 1) ÷ r]. If the deposit goes in at the beginning of the month, multiply the deposit term by (1+r). If the rate is 0, balance = principal + deposit × n. A one-year check with no deposits: 100 at 12% becomes 100 × (1.01)^12, about 112.68.
What the three results are saying
Future value is the balance after the months you asked for. Contributed is only money that came from you: the starting balance plus every deposit. Interest earned is the gap between those two. If the interest line is large, most of the ending balance was growth, not cash you put in.
The yearly table uses the same closed formula at month 12, 24, and so on. It will not match a bank that rounds every single day. Use it to see the shape of the growth. Use the bank's own schedule before you sign anything.
Beginning and end of the month
An end-of-month deposit earns no interest in the month it is deposited. A beginning-of-month deposit earns that month. Over a long period the gap is about one extra month of interest on the deposits, not on the original principal. Principal grows for the full period either way.
A rate that is quoted as APR and compounded monthly belongs in the annual rate field as the nominal yearly percent. If a bank quotes a 7% rate compounded monthly, type 7, not the effective annual rate. The formula applies the monthly slice itself.
Easy mistakes
- Using this page for a loan. Loan interest is charged on a falling balance, and you usually do not add a deposit on top.
- Typing a monthly rate into the annual field. A 0.5% monthly rate is not a 0.5% annual rate.
- Treating the result as a promise. Fees, skipped months, taxes on interest, and a rate that changes are outside the formula.
Questions
Does this include tax on the interest?
No. The balance is pre-tax. If interest is taxable, the spendable amount is lower. You can take the interest figure to the percentage calculator and remove your own tax rate. Sumslip does not know your bracket.
Why does a zero rate not care about deposit timing?
With no interest, money you add is just added. Timing only matters when a balance earns a return.
Can I model a raise in the monthly deposit?
Not in one pass. The deposit is constant. Run the years before the raise, then start a second run with the new balance as principal and the higher deposit.
Related tools
These figures are estimates you can recompute from the formula on the page. They are not a lender quote, a tax bill, a payroll statement, or financial advice.