OneTaskBy Tim King · Updated
Investment Calculator
See How Much Your Monthly Investments Will Be Worth Over Time
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How the Investment Calculator works
This investment calculator projects what a portfolio could be worth. Enter a starting amount, a monthly contribution, an expected annual return and how many years to invest, and it shows the final value, how much you put in, how much came from growth, and a year-by-year breakdown.
Investment calculator formula
The investment calculator compounds monthly. The starting amount grows as a lump sum and the contributions grow as an annuity, where r is the monthly return and n the number of months:
Value = start × (1 + r)^n + monthly × ((1 + r)^n − 1) ÷ r
The return is an assumption, not a promise. Real markets rise and fall year to year, so treat the result as one scenario and try a lower and a higher rate beside it.
Worked example: 500 a month for 20 years
Start with 10,000 and add 500 a month at 7% for 20 years. You contribute 130,000 in total and the portfolio reaches 300,850.72, so 170,850.72, or 56.8% of the final value, is growth.
Worked example: 200 a month for 10 years
With nothing to start and 200 a month at 6% for 10 years, you put in 24,000 and end with 32,775.87. The table below shows how many years of compounding it takes before growth outweighs the money paid in.
Investment reference table
The value of investing 100 a month at annual returns of 4%, 6%, 8% and 10%, after 1 to 25 years.
| Years | 4% | 6% | 8% | 10% |
|---|---|---|---|---|
| 1 | 1,222.25 | 1,233.56 | 1,244.99 | 1,256.56 |
| 2 | 2,494.29 | 2,543.20 | 2,593.32 | 2,644.69 |
| 3 | 3,818.16 | 3,933.61 | 4,053.56 | 4,178.18 |
| 4 | 5,195.96 | 5,409.78 | 5,634.99 | 5,872.25 |
| 5 | 6,629.90 | 6,977.00 | 7,347.69 | 7,743.71 |
| 6 | 8,122.26 | 8,640.89 | 9,202.53 | 9,811.13 |
| 7 | 9,675.42 | 10,407.39 | 11,211.33 | 12,095.04 |
| 8 | 11,291.85 | 12,282.85 | 13,386.86 | 14,618.11 |
| 9 | 12,974.15 | 14,273.99 | 15,742.95 | 17,405.37 |
| 10 | 14,724.98 | 16,387.93 | 18,294.60 | 20,484.50 |
| 11 | 16,547.15 | 18,632.26 | 21,058.04 | 23,886.05 |
| 12 | 18,443.55 | 21,015.02 | 24,050.84 | 27,643.79 |
| 13 | 20,417.21 | 23,544.73 | 27,292.04 | 31,795.01 |
| 14 | 22,471.29 | 26,230.48 | 30,802.26 | 36,380.92 |
| 15 | 24,609.05 | 29,081.87 | 34,603.82 | 41,447.03 |
| 16 | 26,833.91 | 32,109.13 | 38,720.91 | 47,043.64 |
| 17 | 29,149.41 | 35,323.11 | 43,179.72 | 53,226.28 |
| 18 | 31,559.24 | 38,735.32 | 48,008.61 | 60,056.32 |
| 19 | 34,067.26 | 42,357.99 | 53,238.30 | 67,601.56 |
| 20 | 36,677.46 | 46,204.09 | 58,902.04 | 75,936.88 |
| 21 | 39,394.01 | 50,287.41 | 65,035.87 | 85,145.02 |
| 22 | 42,221.22 | 54,622.59 | 71,678.81 | 95,317.38 |
| 23 | 45,163.63 | 59,225.14 | 78,873.11 | 106,554.91 |
| 24 | 48,225.91 | 64,111.58 | 86,664.53 | 118,969.16 |
| 25 | 51,412.95 | 69,299.40 | 95,102.64 | 132,683.34 |
Quick answers
- 100 a month at 8% grows to about 18,400 in 10 years.
- Doubling the monthly amount doubles the final value.
- Over long periods the return rate matters more than the start amount.
- Fees reduce the return: 7% with a 1% fee is roughly 6%.
- Use a lower rate to allow for inflation and see today's money.
FAQ
What return should I use?
It depends on what you invest in. Broad stock indexes have historically returned more than bonds or cash over long periods, but with larger swings. Many people plan with a cautious rate and treat anything above it as a bonus.
Does this include fees and tax?
No. Subtract your yearly fund and platform fees from the return before entering it. Tax on growth depends on the account type and your country, so this calculator shows the value before any tax.
How do I see the result in today's money?
Enter a real return, which is the expected return minus expected inflation. A 7% return with 2.5% inflation is a real return of about 4.5%, and the result is then in roughly today's purchasing power.
Are contributions made at the start or end of the month?
The calculator adds each contribution at the end of the month, which is the usual convention. Paying in at the start of each month would give a slightly higher final value.
See also: all Investing tools, Pay, Bills, Property, Debt, Saving.
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