Project the future value of savings with compound interest and regular contributions, separating the money you put in from the growth.
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10,000 at 5% for 10 years grows to 16,288.95 with yearly compounding and 16,470.09 with monthly compounding. Adding 100 a month to the same 10,000 gives 31,998.32: 22,000 contributed and 9,998.32 in growth.
In each period the balance is multiplied by the annual rate divided by the number of periods per year, and the contribution is added at the end of that period. The number of periods is the years multiplied by the periods per year, so monthly compounding runs 12 periods a year. Contributed money is the starting amount plus every contribution, and growth is the final balance minus that.
The contribution is per period, not per year: keeping 100 but switching from monthly to quarterly means 100 every quarter. A constant rate is an assumption, real returns vary, and fees, taxes and inflation are not included. Deposits are added at the end of each period, so the last one earns nothing and start-of-period deposits would give slightly more.
The contribution field is the amount added in each selected period, not per year. With 10,000 at 5% for 10 years, adding 100 monthly produces 31,998.32, of which 22,000 is money you put in and 9,998.32 is growth. If you switch the period to quarterly without changing the contribution, the tool adds 100 per quarter instead of 100 per month. Convert a yearly savings plan to the matching amount per period before calculating.
Without contributions, 10,000 at 5% for 10 years grows to 16,288.95 with yearly compounding and 16,470.09 with monthly compounding, because monthly growth begins earning interest sooner. Contributions are added at the end of each period, so the final deposit earns nothing. Starting from zero and saving 200 a month at 4% for 20 years gives 73,354.93: 48,000 in deposits and 25,354.93 in interest. Deposits made at the start of each period would produce a slightly higher balance.
A constant rate is a simplification. Real investments fluctuate, and fees, taxes and inflation reduce what you keep. A negative rate can illustrate decline: 10,000 at −2% compounded yearly for 5 years falls to 9,039.21. Try a cautious rate and an optimistic rate side by side instead of relying on one projection. The result is arithmetic, not a forecast or recommendation, and savings accounts may calculate interest daily or credit it on different dates.
| Input | Result |
|---|---|
10,000 · 0 · 5% · 10 y · 1/y | 16,288.95 |
10,000 · 0 · 5% · 10 y · 12/y | 16,470.09 |
10,000 · 100 · 5% · 10 y · 12/y | 31,998.32 (22,000 + 9,998.32) |
0 · 200 · 4% · 20 y · 12/y | 73,354.93 (48,000 + 25,354.93) |
10,000 · 0 · −2% · 5 y · 1/y | 9,039.21 |
Less than many people expect. Without contributions, 10,000 at 5% for 10 years reaches 16,288.95 compounded yearly and 16,470.09 compounded monthly, because monthly growth starts earning sooner. The rate, the amount and the number of years matter far more than the frequency.
The result separates the two. Saving 200 a month from zero at 4% for 20 years ends at 73,354.93, of which 48,000 is deposits and 25,354.93 is interest. Over long periods the growth share rises, which is why starting earlier usually matters more than a slightly higher rate.
Yes. Enter a negative rate: 10,000 at −2% compounded yearly for 5 years falls to 9,039.21. For a rough after-inflation figure, subtract expected inflation from your expected return and enter the result. The projection is arithmetic, not a forecast or investment advice.
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