Investment growth calculator

What this calculator does

It shows what a lump sum plus a monthly contribution could grow into over the years you choose, and it splits the result into the part you paid in and the part compounding added. That second part is the whole argument for starting early. The chart lets you watch the gap widen year by year, which is more persuasive than any slogan about it.

How this calculator works

The maths is standard compound interest: your starting amount grows at the annual rate you set, compounded monthly, and every monthly contribution starts compounding from the month it lands. The rate is yours to choose. The honest move is to use a figure net of inflation and fund charges, because the calculator will not subtract them for you.

What it deliberately leaves out: tax, fund and platform fees, rising contributions, and risk itself. A steady line on a chart is a smoothed fiction; real portfolios spend years above it and years below it, and only land near it if you stay invested the whole way through. The tool shows the destination the rate implies, not the weather on the road.

When to use it (and when not)

Use it before you commit to a monthly amount, to check the plan actually reaches the goal, and again whenever you are tempted to stop, to see what cutting the last years of compounding would cost. Do not use it to compare products; it knows nothing about fees. If your goal has a deadline attached, the savings goal calculator asks the better question: what monthly amount gets you there in time.

This calculator is educational, not financial advice, and it names no product, fund, or provider. The projection is illustrative and assumes the steady return you chose. Investment values can fall as well as rise, and you could get back less than you put in. Actual returns depend on the funds you pick, their performance, and their charges; past performance tells you little about the future. For decisions about your own money, talk to a regulated adviser in your market.