FT MarketWatch

Investment Growth Calculator

Written by Greg, founder of FTMarketWatch — a former licensed commodities trader, self-directed investor since. Not a licensed financial advisor.

Last reviewed: September 2, 2026

What this tool does: estimates how your money could grow over time based on a starting amount, regular monthly contributions, your time horizon and an assumed average annual rate of return.

Enter your assumptions

$
What you already have invested or plan to invest as a lump sum.
$
How much you plan to add each month.
How long you expect to leave the money invested.
%
This is a simplifying assumption, not a prediction.

This calculator is for educational illustration only. Actual returns will vary, and no future performance is guaranteed.

How to interpret the numbers

The main takeaway from this kind of calculation is usually not the exact dollar amount, but the relationship between time, contributions and return assumptions.

  • On Dollar-Cost Averaging we look at how regular contributions help smooth the ride.
  • On Asset Allocation we discuss how your stock/bond mix influences the kinds of returns – and volatility – you might experience.
  • On Investing 101 we put these pieces together into a simple, written plan.

Use this calculator as a rough map, not a precise forecast. If changing one input (such as saving a little more each month) materially changes the outcome, that can be a useful planning insight even though no one knows future returns exactly.

The math is currency-neutral: you can treat the amounts as dollars, pounds, euros or another currency as long as you use the same currency for every amount.

How to use the result

The calculator separates the money you contribute from the estimated growth generated by the return assumption. Try more than one return rate rather than treating a single result as a forecast. A lower-return scenario can show how much of your goal depends on saving more versus earning more.

Example

If you start with $10,000, add $500 each month and assume a 6% average annual return, the calculator estimates the future value using monthly compounding. Change the return, contribution or time horizon to see which assumption has the biggest effect.

What this calculator does not include

  • Taxes, trading costs or fund expenses.
  • Inflation or changes in purchasing power.
  • Irregular contributions or withdrawals.
  • Year-to-year market volatility.

For a real plan, it is often useful to test a conservative case as well as an optimistic one.

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