What is an investment growth calculator?
An investment growth calculator estimates a future portfolio value from an initial amount, a monthly contribution and an expected annual return you enter. This NumberMotive version compounds monthly and can raise the contribution once per year. It also shows total contributions, estimated growth, the horizon and the share of the projected value that came from money put in.
The result is an educational estimate from the numbers you type. It is not financial advice, investment advice, a market forecast, portfolio management, a guaranteed return or official retirement planning.
How investment growth is modeled here
The model uses monthly compounding only. The annual return is divided by 12. The initial investment grows as a lump sum. Monthly contributions are treated as deposits at the end of each month (an ordinary annuity). The horizon is the years you enter, converted to months.
A yearly contribution increase, when greater than 0%, multiplies the monthly contribution by (1 + increase) at the start of each new year. The first 12 months use the amount you typed. Year 2 uses that amount times (1 + increase), and so on. 0% keeps the contribution constant.
The formulas this calculator uses
Monthly rate r = expected annual return ÷ 100 ÷ 12
Months n = investment horizon × 12.
Initial after growth when r is greater than 0 and n is greater than 0:
initial × (1 + r)^n
Contribution growth when the yearly increase is 0% and r is greater than 0:
PMT × [((1 + r)^n − 1) ÷ r]
When the yearly increase is greater than 0%, each year uses its own monthly amount: PMT × (1 + g)^year. That year’s deposits grow as a 12-month annuity (or a shorter remainder) and then continue compounding until the end of the horizon.
When the expected return is 0%, the initial amount stays unchanged and contributions add as cash only. When years are 0, the projected value equals the initial investment. The calculator does not divide by zero and does not return NaN or Infinity.
Projected portfolio value = grown initial + grown contributions.
Total contributions = the cash added after the start, including any yearly increases. The initial investment is shown separately.
Estimated growth = projected value − initial − total contributions.
Contribution percentage = (initial + total contributions) ÷ projected value, or 100% when the projected value is $0.00.
Worked example
With a $10,000.00 initial investment, a $500.00 monthly contribution, a 7% expected annual return, 10 years and a 0% yearly increase, there are 120 months. The initial amount grows to $20,096.61. Contributions grow to $86,542.40. The projected portfolio value is $106,639.02. Total contributions are $60,000.00. Estimated growth is $36,639.02. Contribution percentage is 65.64%.
Raising the contribution by 3% each year keeps the same initial growth and lifts later deposits. Total contributions become $68,783.28. The last modeled monthly contribution is $652.39. The projected portfolio value is $117,640.78. None of those inputs is a recommended investment or a guaranteed return.
What this calculator does not include
- Inflation, taxes, account fees or trading costs
- Asset allocation, rebalancing or portfolio management
- Dividends as a separate cashflow, capital-gains timing or wash sales
- Social Security, pensions, employer match or retirement-plan rules
- Withdrawal, spending or sequence-of-returns modeling
- A recommended return, product or contribution schedule
Limitations of this calculator
- Results are estimates based only on the numbers you enter.
- The model assumes a constant monthly rate and a contribution that changes only at each new year.
- A 0% return, 0% increase or a 0-year horizon does not produce Infinity or NaN.
- Very large combinations are rejected when a result leaves the safe numeric range.
- Scenarios are not saved, emailed or sent to analytics.
Frequently asked questions
What is an investment growth calculator?
It estimates a future portfolio value from an initial investment, a monthly contribution and an expected annual return you enter. This NumberMotive version compounds monthly and can raise the contribution once per year. It is an educational worksheet, not a recommended investment.
How is the projected portfolio value calculated?
The initial amount grows as a lump sum with monthly compounding. Monthly contributions grow as an ordinary annuity, with an optional yearly step-up. The two grown amounts are added. With $10,000.00, $500.00 each month, 7%, 10 years and a 0% increase, the projected value is $106,639.02.
What expected annual return should I enter?
Enter the annual percentage you want to model. The calculator does not look up market returns, recommend an allocation or guarantee a result. 0% is valid and treats growth as $0.00.
How does monthly compounding work here?
The annual return is divided by 12. There are 12 modeled periods in each year. The investment horizon is multiplied by 12 to get the number of months. Other frequencies are not offered on this page.
How does the yearly contribution increase work?
The increase raises the monthly contribution at the start of each new year. The first 12 months use the amount you typed. A 3% increase on $500.00 makes later years larger, and the last modeled month in the 10-year example is $652.39.
What if the yearly contribution increase is 0%?
0% is the default. The monthly contribution stays constant for the whole horizon. The contribution math then matches a standard monthly annuity.
What if the expected annual return is 0%?
A 0% return is valid. The initial investment stays at the entered amount. Monthly contributions add as cash only, including any yearly increases. Estimated growth is $0.00.
What if the monthly contribution is $0?
A $0.00 monthly contribution is valid. Only the initial investment compounds. Total contributions are $0.00. A yearly increase has no effect because there is no contribution to raise.
What if the initial investment is $0?
A $0.00 starting amount is valid. Only monthly contributions grow. The projected value equals the grown contributions.
What if the investment horizon is 0 years?
A 0-year horizon is valid. The projected value equals the initial investment. No monthly deposits are modeled. The calculator does not divide by zero and does not return Infinity or NaN.
How is total contributions calculated?
Total contributions are the cash added after the start. If the yearly increase is 0%, that is the monthly amount times the number of months. If the increase is greater than 0%, later years add larger monthly amounts. The initial investment is shown separately.
How is estimated growth calculated?
Estimated growth is the projected value minus the initial investment minus total contributions. It is the modeled gain above money put in. It is not a guaranteed return.
How is contribution percentage calculated?
Contribution percentage is the initial investment plus total contributions, divided by the projected value. If the projected value is $0.00, the percentage is 100%. It describes the mix in this worksheet, not a recommended savings rate.
Does this include taxes, fees, inflation or portfolio management?
No. There is no tax, fee, inflation, rebalancing or portfolio-management model. The worksheet uses only the amounts, rate, years and optional increase you type.
Is the expected return a guaranteed return or a market forecast?
No. The rate is a planning assumption you type. Markets vary. The calculator does not forecast markets, guarantee a return or recommend an investment.
Is this result financial advice or official retirement planning?
No. It is an educational estimate from numbers you chose. It is not financial advice, investment advice, portfolio management or official retirement planning.
Last reviewed August 24, 2026 (UTC).