Investment Growth Calculator
Model investment contributions that rise or fall each year, and compare constant-return scenarios.
Projected investment value
Constant hypothetical return, month-end contributions and anniversary contribution changes. No volatility path, tax, fees or inflation. Returns are not forecasts. A −100% contribution change stops deposits after the first year.
Contributions and projected growth by year
Constant hypothetical returns with month-end contributions. The table separates deposited capital from modelled growth; negative growth means the projected balance is below contributions.
| Year | Contributed capital | Projected balance | Growth or loss |
|---|---|---|---|
| 0 | $10,000.00 | $10,000.00 | $0.00 |
| 1 | $12,400.00 | $12,954.52 | $554.52 |
| 2 | $14,872.00 | $16,130.39 | $1,258.39 |
| 3 | $17,418.16 | $19,540.91 | $2,122.75 |
| 4 | $20,040.70 | $23,200.07 | $3,159.36 |
| 5 | $22,741.93 | $27,122.65 | $4,380.72 |
| 6 | $25,524.18 | $31,324.24 | $5,800.06 |
| 7 | $28,389.91 | $35,821.27 | $7,431.36 |
| 8 | $31,341.61 | $40,631.08 | $9,289.47 |
| 9 | $34,381.85 | $45,771.94 | $11,390.08 |
| 10 | $37,513.31 | $51,263.12 | $13,749.81 |
Formula checked · NumberSwift · Review process
For informational purposes only. Results are estimates and do not constitute financial advice.
How this calculator works
Monthly contributions stay fixed during each year, then change by the entered annual percentage on the next anniversary. The effective annual return is converted to an equivalent monthly rate; contributions arrive at month end. The projection separates all invested capital from modelled growth, which can be negative. Two nearby return scenarios show sensitivity to assumptions. Unlike Compound Interest, this tool explicitly models a changing contribution schedule and uses an effective annual return rather than a nominal compounding frequency.
Formula
Monthly return = (1 + effective annual return/100)^(1/12) − 1. Monthly contribution in year y = first-year contribution × (1 + annual contribution change/100)^y. Each month: balance = previous balance × (1+r) + contribution.
Assumptions & limitations
Constant hypothetical return, month-end contributions and anniversary contribution changes. No volatility path, tax, fees or inflation. Returns are not forecasts. A −100% contribution change stops deposits after the first year.
Sources & reference material
- OpenStax: annuities ↗
Background for equal-period cash flows; not a forecast of returns or a lender APR disclosure.
Worked example
With no starting investment, 100 monthly contributions, 10% annual contribution growth and 0% return for 2 years, the first year adds 1,200 and the second adds 1,320. Final value and contributed capital both equal 2,520; investment growth is zero.
Our approach to calculations ↗Common questions
Does the entered return predict market performance?
No. It is a constant-rate hypothetical assumption and does not model volatile yearly returns.
When do contributions increase?
After every complete year. The first twelve contributions use the initial monthly amount; the next twelve apply one annual increase.
Can I model negative returns or decreasing contributions?
Yes. Annual returns must exceed −100%, and contribution change can range from −100% to 100%. The growth output can show a loss.
How does this differ from Retirement Savings?
This tool explores a changing investment contribution schedule. Retirement Savings compares a constant monthly plan with a user-chosen retirement target.