Investment Calculator
Project the future value of any investment with regular contributions and compound growth.
£5,000 invested for 20 years at 7%, with £2,400 added each year, grows to £124,379 — £71,379 of that is investment return.
Show your working
If the return were different
| Annual return | End balance | Investment return |
|---|---|---|
| 5% | £95,770 | £42,770 |
| 7% | £124,379 | £71,379 |
| 9% | £163,623 | £110,623 |
Same starting amount, same contributions, same term — only the rate of return changes.
Assumptions
- Returns are assumed steady; real markets do not deliver the same figure every year.
- Contributions continue unchanged for the whole period.
- Charges, platform fees and tax are not deducted.
- Inflation is not applied, so these are cash amounts rather than spending power.
Year-by-Year Breakdown
| Year | Opening Balance | Contributions | Interest Earned | Closing Balance |
|---|
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Investment facts
- What does a two-point difference in return do?
- A great deal over time. On the same contributions, 2 percentage points either side of your rate changes the end balance by tens of thousands — the scenario table above shows your own figures.
- Does when I contribute matter?
- Yes, slightly. Contributing at the start of each period gives every payment one extra period of growth, which compounds over a long horizon.
- Are these figures before or after charges?
- Before. Platform fees, fund charges and tax are not deducted, so treat the result as a gross projection.
- Why assume a steady return?
- Because no one can predict the sequence. Real returns vary year to year, and a poor run early on hurts more than the same run later.
How Compound Investment Growth Works Over Time
Contribution timing
Beginning-of-period contributions earn one extra compounding period of interest. Over decades this difference compounds meaningfully — each contribution effectively earns one additional period of return versus end-of-period.
Compounding frequency
The more frequently returns compound, the faster your investment grows. Monthly compounding slightly outperforms quarterly or annual at the same stated rate, because you earn returns on returns sooner. The compound interest calculator isolates compounding frequency in detail.
Regular contributions
Consistent contributions often matter more than the initial lump sum over long periods. Even modest additions compound significantly over time — this is the snowball effect of investing regularly. Use the ROI calculator to measure the overall return on a completed investment.
Time in the market
Starting early makes a dramatic difference. At 7% per year, an investment doubles roughly every 10 years (Rule of 72). A 10-year head start can more than double your final balance at the same monthly contribution. The average return calculator works out your actual annual return from past figures.
Worked example
Starting with £5,000 and contributing £200 per month at 7% annual return over 20 years: contributions total £53,000 but the investment grows to approximately £108,000 — the remaining £55,000 comes entirely from compound growth. Starting 10 years later with the same monthly amount would yield only around £34,000.
Related calculations
For regular deposits into savings rather than an investment, use the savings calculator. To measure something you already hold, the ROI calculator annualises the return, and if a pay rise is funding it the pay rise calculator shows what actually reaches your account.
Why Real Portfolios Miss the Projection
Charges compound against you
A platform fee plus a fund's ongoing charge might total 0.6% a year — small next to an assumed 7% return, but it compounds in exactly the same way the growth does. Over 30 years, 7% net of 0.6% is not 0.6% less money; it is roughly 15% less, because every year's fee also costs you the growth that fee would have earned. The cleanest way to model this is to enter your expected return minus total charges rather than the headline figure.
A fixed rate is a model, not a forecast
This calculator applies the same return every period. Real markets do not: they deliver a scatter of gains and losses that happen to average out. For a lump sum left alone the end result is similar, but if you are withdrawing, the order of returns matters enormously — a bad first few years while you draw down does lasting damage that a good average cannot repair. That is sequence-of-returns risk, and it is why drawdown planning needs the money-duration calculator rather than a smooth projection.
Tax wrappers change the arithmetic
Investments held in a Stocks and Shares ISA grow free of UK capital gains and dividend tax, and a pension adds tax relief on the way in while taxing most of the income on the way out. Outside a wrapper, gains above the annual exempt amount and dividends above the dividend allowance are taxable, so the return you keep is lower than the return you earn. Allowances and limits are set by HMRC and change periodically — check GOV.UK for current figures. This calculator projects gross growth only.
Contributions usually beat cleverness early on
Early on, the balance is dominated by what you put in rather than by the rate. Someone contributing £300 a month at 5% stays ahead of someone contributing £200 a month at 8% for about 22 years — at year 10 they hold roughly £46,600 against £36,600 — before the higher rate finally overtakes them. Rate compounds harder as the pot grows, but over most people's saving horizon the contribution you control matters more than the return you cannot.
Evidence & Methodology
How This Page Is Grounded
Method
Compounds the opening balance and regular contributions at the selected frequency to project a future value.
Important limitation: The return is assumed constant; actual investments fluctuate and can lose value.
Primary Sources
- Compound Interest Calculator Investor.gov — U.S. Securities and Exchange Commission
- Investing: an introduction MoneyHelper
Quality Checks
Checked with no-contribution, zero-return and regular-contribution examples.
See how sources are selected and corrections are handled in our Editorial & Calculation Methodology, and which automated checks this page has to pass in How We Test.
Frequently Asked Questions
Does it matter when within each period I make my investment contributions?
Yes — beginning-of-period contributions earn one extra compounding period of return compared to end-of-period contributions. Over decades this difference compounds meaningfully, so the investment calculator lets you compare both timing options.
Why do regular contributions matter so much for investment growth?
Consistent contributions often matter more than the initial lump sum over long periods — even modest additions compound significantly over time thanks to the snowball effect of investing regularly. The investment calculator shows your final balance broken down by initial deposit, total contributions, and interest earned.
How much does starting early affect my final investment balance?
At 7% per year, an investment doubles roughly every 10 years (the Rule of 72), so a 10-year head start can more than double your final balance at the same monthly contribution. Use the investment calculator to compare different time horizons side by side.