Investment Growth Calculator

Project investment growth with a starting balance, monthly contributions and an assumed annual return. The result updates as you type so you can compare scenarios quickly.

The method

How it is worked out

A = P(1 + r)^N + C × (1 + r)^N − 1r

P: Starting investment
C: Monthly contribution
r: Monthly return, annual ÷ 12
N: Months, years × 12

Keep in mind

What it leaves out

Market swingsReal returns go up and down. This assumes the same return every month.
Fees and taxPlatform fees, fund charges and tax on gains aren't included.
InflationThe result is in future money, which buys less than today's.

Use the calculator to compare scenarios rather than as a guaranteed forecast.

About the Investment Growth Calculator

See how an initial investment might develop alongside monthly top-ups. The tool is helpful for retirement or medium-term planning when you need to distinguish the amount contributed from the growth implied by an assumed return.

How it works and an example to tryShow less

How to use the result

The starting balance and each monthly contribution are compounded using the annual return divided into monthly periods. The year-by-year chart shows the value produced by that constant-return assumption. Real returns fluctuate, and a forecast cannot promise a future portfolio value; charges, tax and inflation are left out of the calculation.

Example to try

Set a ten-year period and a 4% annual return, then compare the forecast with a longer holding period at the same return. Next change only the monthly top-up. The differences show how sensitive the estimate is to time and saving behaviour, not what a market will deliver.

Put it to work

Try it on a real situation

Load an example

What moves the result most

Worked out from your figures above. Tap a row to try it.

Who uses it, and when

Pension savers checking whether contributions are on track, people comparing a longer time horizon against a higher contribution, and advisers illustrating why starting early matters more than picking the perfect fund.

Mistakes worth avoiding

Using one steady return and forgetting that a bad early sequence of years changes the outcome.
Leaving charges out; a one-percent annual fee removes a large slice of thirty-year growth.
Stopping contributions when markets fall, which the model cannot show but real portfolios feel.

Questions

What does the Investment Growth Calculator do?

Project investment growth with a starting balance, monthly contributions and an assumed annual return.

How should I use the result?

Does TechBullion store the information I enter?

The core calculation or transformation runs in your browser. Normal website security and analytics may still record page-level events, but the tool does not need to create a public record from your inputs.

What mistakes do people make with an investment growth calculator?

Using one steady return and forgetting that a bad early sequence of years changes the outcome. Leaving charges out; a one-percent annual fee removes a large slice of thirty-year growth. Stopping contributions when markets fall, which the model cannot show but real portfolios feel.

Is the result guaranteed?

No. Use the result as a practical check or planning aid and verify important decisions with the relevant primary source, provider or professional advice.

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