Investment Calculator
Project how your investment grows over time with compound returns and regular contributions.
Your investment
About the Investment Calculator
An investment calculator answers the question every saver and investor eventually asks: if I put this money in and keep adding to it, what could it be worth in the future? Enter a starting amount, an optional regular contribution, an expected annual return and a timeframe, and it projects the future value — separating how much you contributed from how much was earned through growth.
The engine behind the projection is compounding: returns earned in early years themselves earn returns later, so growth accelerates the longer the money stays invested. This is why time in the market is so powerful, and why the same monthly contribution started ten years earlier can end up worth dramatically more. The calculator makes that effect visible with a year-by-year breakdown and chart.
Use it to set realistic goals — a retirement pot, a house deposit, a child’s education — and to test how sensitive the outcome is to your assumptions. Nudging the contribution up, extending the timeframe, or assuming a slightly different return all reshape the result instantly. Remember that real investment returns vary year to year and are not guaranteed; use the figure as a planning projection, not a promise. Everything is calculated privately in your browser.
Looking for more options? Open the full Compound Interest Calculator — it’s the same tool with every feature.
Frequently Asked Questions
How does an investment calculator work?
It applies compound growth to your starting amount and any regular contributions, using your expected annual return over the timeframe you set. Each period’s growth is added to the balance so future growth is earned on a larger sum — the compounding effect — and the result is your projected future value.
What return rate should I use?
Use a realistic long-run estimate for the type of investment you are modelling rather than an optimistic best case. Because returns vary year to year and are never guaranteed, it is wise to try a conservative and an optimistic rate to see the range of possible outcomes.
How much difference do regular contributions make?
A great deal, especially over long periods, because each contribution has more time to compound. Adding even a modest monthly amount can substantially increase the final value. Enter different contribution levels in the calculator to see the impact on your projected total.
Understanding Investment Growth
The power of compounding
Compounding is the engine of long-term investing: the returns you earn are reinvested and themselves go on to earn returns. Early growth looks modest, but because each year builds on a larger base, the curve steepens over time — the bulk of an investment’s final value often comes from growth in the later years. This is why starting earlier, even with smaller amounts, can beat starting later with more.
Contributions and time horizon
Two of the biggest levers on your final balance are how much you add regularly and how long you stay invested. Regular contributions feed the compounding machine, and a longer horizon gives every pound more time to grow. Stretching the timeframe or nudging up the monthly amount typically moves the projection far more than chasing a slightly higher return — and is far more within your control.
Returns are projections, not promises
Real investments fluctuate; they do not deliver a smooth, fixed return every year. A projection assumes an average rate, but actual results vary and capital can fall as well as rise. Inflation also erodes future spending power, so a balance years away buys less than the same figure today. Treat the output as a planning guide, model a conservative as well as an optimistic rate, and remember that diversification manages — but never removes — risk.