Investment Growth Calculator: See How Contributions Could Compound
This investment growth calculator estimates how a starting balance and regular monthly contributions could grow at an assumed annual return. It separates the money you put in from the growth it could earn, shows an inflation-adjusted value, and compares lower and higher return scenarios.
Investment Growth Calculator
Estimated ending balance
Under these assumptions, $10,000.00 plus $500.00 a month at an estimated 6.00% annual return could grow to $258,790.67 over 20 years, with $128,790.67 coming from investment growth.
- Total contributions
- Investment growth
- Inflation-adjusted ending value
- Share from contributions
- Share from growth
Scenario Comparison
Illustrative rates chosen by Fin Loom: your return 2 percentage points lower and higher. They are not forecasts.
Conservative (4.00%)
$203,832.10Base (6.00%)
$258,790.67Higher-return (8.00%)
$331,109.11Contributions vs Growth
Balance (solid)Total contributions (dashed)
| Year | Contributions That Year | Total Contributions | Investment Growth | Ending Balance | Inflation-Adjusted Balance |
|---|---|---|---|---|---|
| 1 | $6,000.00 | $16,000.00 | $763.26 | $16,763.26 | $16,763.26 |
| 2 | $6,000.00 | $22,000.00 | $1,932.32 | $23,932.32 | $23,932.32 |
| 3 | $6,000.00 | $28,000.00 | $3,531.53 | $31,531.53 | $31,531.53 |
| 4 | $6,000.00 | $34,000.00 | $5,586.68 | $39,586.68 | $39,586.68 |
| 5 | $6,000.00 | $40,000.00 | $8,125.15 | $48,125.15 | $48,125.15 |
| 6 | $6,000.00 | $46,000.00 | $11,175.92 | $57,175.92 | $57,175.92 |
| 7 | $6,000.00 | $52,000.00 | $14,769.74 | $66,769.74 | $66,769.74 |
| 8 | $6,000.00 | $58,000.00 | $18,939.19 | $76,939.19 | $76,939.19 |
| 9 | $6,000.00 | $64,000.00 | $23,718.81 | $87,718.81 | $87,718.81 |
| 10 | $6,000.00 | $70,000.00 | $29,145.20 | $99,145.20 | $99,145.20 |
| 11 | $6,000.00 | $76,000.00 | $35,257.17 | $111,257.17 | $111,257.17 |
| 12 | $6,000.00 | $82,000.00 | $42,095.87 | $124,095.87 | $124,095.87 |
| 13 | $6,000.00 | $88,000.00 | $49,704.89 | $137,704.89 | $137,704.89 |
| 14 | $6,000.00 | $94,000.00 | $58,130.44 | $152,130.44 | $152,130.44 |
| 15 | $6,000.00 | $100,000.00 | $67,421.53 | $167,421.53 | $167,421.53 |
| 16 | $6,000.00 | $106,000.00 | $77,630.09 | $183,630.09 | $183,630.09 |
| 17 | $6,000.00 | $112,000.00 | $88,811.16 | $200,811.16 | $200,811.16 |
| 18 | $6,000.00 | $118,000.00 | $101,023.09 | $219,023.09 | $219,023.09 |
| 19 | $6,000.00 | $124,000.00 | $114,327.74 | $238,327.74 | $238,327.74 |
| 20 | $6,000.00 | $130,000.00 | $128,790.67 | $258,790.67 | $258,790.67 |
Assumptions
- The return is a constant average; real returns vary from year to year and can be negative.
- The annual return converts to an equivalent monthly rate, (1 + r)^(1/12) - 1.
- Contribution increases apply once a year, starting in year 2.
- Fees, taxes, and withdrawals are not included.
- The inflation-adjusted value divides the ending balance by (1 + inflation) for each year.
Educational estimate only. This calculator uses the assumptions you enter to illustrate a possible financial outcome. It does not predict future investment performance, interest rates, inflation, taxes, market prices, or financial results. Actual outcomes may differ.
How the Investment Growth Calculator Works
The calculator works month by month. It converts the annual return you enter into an equivalent monthly rate:
Monthly rate = (1 + annual return)^(1/12) − 1
Each month, the balance earns that rate and your contribution is added at the start or end of the month. Using the equivalent monthly rate means twelve months of growth add up to exactly the annual return you entered, rather than slightly more, which is what dividing by 12 would produce.
With the opening example, $10,000 plus $500 a month at an assumed 6% annual return for 20 years could reach about $258,790.67. Of that, $130,000 is money contributed and about $128,790.67 is investment growth. These are Fin Loom calculations under constant-return assumptions.
Advanced Options
The advanced options let you set three things:
- Contribution Timing: Money added at the start of each month has one extra month to grow compared with money added at the end.
- Annual Contribution Increase: Raises the monthly contribution once a year, which can model saving more as income rises.
- Inflation Rate: Converts the ending balance into today's dollars by dividing it by (1 + inflation) for each year, so you can see estimated buying power, not just the nominal figure.
Reading the Scenarios and Chart
The scenario cards show the same plan at your return, 2 percentage points lower, and 2 percentage points higher. Those spreads are illustrative choices, not forecasts, and they show how sensitive a long-term estimate is to the return assumption.
The chart plots the balance and total contributions over time. The widening gap between the two lines is investment growth. The year-by-year table lists the contributions, growth, and balance for every year.
What This Calculator Does Not Include
Real investments do not earn a steady return. Prices can fall for long stretches, and the order of good and bad years affects results, especially when money is being added or withdrawn. The calculator also leaves out fund fees, trading costs, and taxes, which can reduce growth meaningfully over decades. The comparison of index fund vs mutual fund costs shows how even small fee differences add up.
Whether money should be invested at all depends on when it is needed. Saving vs investing explains why short-term money usually belongs in savings rather than in assets whose value can drop.
More Fin Loom Calculators
This tool is part of Fin Loom's set of financial calculators and reference tools, which covers inflation, compound interest, investment growth, dividends, withdrawals, capital gains tax, and stock trades.
Frequently Asked Questions
What Return Should I Enter?
Any return you enter is an assumption, not a prediction. Testing a lower and higher rate, as the scenario cards do, shows how much the estimate depends on that single input.
Why Does Contribution Timing Change the Result?
Money added at the start of each month earns one more month of growth than money added at the end, so the ending balance is slightly higher.
What Does the Inflation-Adjusted Value Mean?
It estimates the ending balance in today's dollars by removing the inflation rate you enter, which gives a rough sense of future buying power.