Investment Calculator
Calculate the future value of an investment with one-time or recurring contributions, and see the effect of different return rates.
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How to use this calculator
FV = future value, P = principal, r = annual rate, n = compounding frequency, t = years, PMT = periodic addition.
- 1
Enter your starting investment amount.
- 2
Enter how much you will add each month.
- 3
Enter the annual return rate you want to test.
- 4
Select how often interest is compounded.
- 5
See the projected portfolio value and total gains.
Frequently asked questions
What formula does this tool use?
This tool values the starting amount and the monthly additions separately and adds the two. The starting amount grows by (1 + rate ÷ n)^(n × years), where n is the compounding frequency you select. Each monthly addition grows at the monthly rate that matches that frequency, (1 + rate ÷ n)^(n ÷ 12) − 1, using the annuity formula for the number of months.
When in the month is each addition counted?
Month end. The first deposit therefore earns interest for one month fewer than the full period, and the last deposit earns none. Over 20 years that means 240 deposits. A start-of-month schedule would give a somewhat higher balance, but this tool does not offer it.
How much does the compounding frequency change the result?
Only the starting amount and the monthly rate are affected, so the gap is modest. With $10,000 to start, $200 a month, a 6% rate and 15 years, annual compounding gives $81,347.96, quarterly $82,448.68, monthly $82,704.68 and daily $82,830.04. Total invested is $46,000 in every case.
What happens when the return is 0%?
Nothing grows, so the final value equals what you put in. With $5,000 to start, $300 a month and 10 years, the tool shows $41,000.00 invested, $0.00 of gains and a total return of 0.0%. An explicit 0 is treated as 0%, not as a missing value.
What does Total Return mean here?
Total Return is investment gains divided by total invested, times 100, over the whole period. It is not a yearly rate. The default plan shows 161.5% over 20 years, which says nothing by itself about the annual rate. If nothing is invested at all, the field shows n/a rather than an error.
Are fees, taxes or inflation included?
No. The projection applies one constant rate for every year and subtracts nothing: no fund charges, no platform fees, no tax on gains or dividends, and no adjustment for rising prices. To approximate a net result, enter a rate that is already reduced by the costs you want to test.
What can this tool not model?
It cannot handle contributions that change over time, withdrawals, one-off top-ups, or a rate that changes from year to year. Fractional periods are rounded to the nearest whole month for the monthly additions. For a lump sum alone, the mutual fund calculator is simpler.
Investment calculator: a starting sum plus monthly additions
How the projection is put together
Two pots are tracked separately. The starting sum compounds at the frequency you choose, from annual to daily. The monthly additions land at month end and compound at the monthly rate that corresponds to that frequency. Adding the two pots gives the final value, and total invested is the starting sum plus the number of months times the monthly amount. Everything else, gains and total return, is derived from those two figures.
Worked example: the built-in 20-year plan
The figures built into this tool are $5,000 to start, $300 a month, an 8% rate, 20 years and monthly compounding. Running them gives a final portfolio value of $201,340.14 against $77,000.00 invested, so gains are $124,340.14 and total return is 161.5%. Remove the monthly additions and compare: $10,000 at 8% for 20 years with monthly compounding finishes at $49,268.03, a gain of $39,268.03 or 392.7% on the amount invested. The outputs illustrate the inputs only; they are not forecasts or advice.
How compounding frequency moves the answer
The next table keeps the plan fixed at $10,000 to start, $200 a month, 6% and 15 years, and changes only the compounding frequency. The invested total never moves, so every difference in the last two columns comes from how often the starting sum and monthly rate are credited.
| Compounding | Final value | Gains | Total return |
|---|---|---|---|
| Annually | $81,347.96 | $35,347.96 | 76.8% |
| Quarterly | $82,448.68 | $36,448.68 | 79.2% |
| Monthly | $82,704.68 | $36,704.68 | 79.8% |
| Daily | $82,830.04 | $36,830.04 | 80.1% |
Monthly additions only, and the zero-rate case
Start with nothing and add $500 a month at 6% for 10 years: the final value is $81,939.67 on $60,000.00 invested, gains of $21,939.67 and a total return of 36.6%. Set the rate to 0 instead and the same habit simply stacks up. With the $5,000 start and $300 a month over 10 years the balance is $41,000.00, identical to the invested total, which is a useful baseline for judging how much of any other result comes from the rate.
What the projection leaves out
Charges, taxes and inflation are absent, the rate is the same every year, and the contribution never changes. A real portfolio can lose value in a given year, and none of that variability appears here. Treat the output as arithmetic that shows how the length of time, the monthly amount and the rate you type interact, and change one input at a time to see which one matters most.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →