UK Investment calculator
Project how an investment grows with monthly contributions and market returns — choose an index preset or your own rate, in nominal or inflation-adjusted terms.
Investment plan
Presets reflect long-run historical averages before fees and tax. Markets are volatile — real returns vary widely year to year.
| Year | Contributed | Balance |
|---|---|---|
| 1 | £16,000.00 | £17,329.91 |
| 2 | £22,000.00 | £25,427.37 |
| 3 | £28,000.00 | £34,372.73 |
| 4 | £34,000.00 | £44,254.79 |
| 5 | £40,000.00 | £55,171.63 |
| 6 | £46,000.00 | £67,231.60 |
| 7 | £52,000.00 | £80,554.41 |
| 8 | £58,000.00 | £95,272.29 |
| 9 | £64,000.00 | £111,531.33 |
| 10 | £70,000.00 | £129,492.90 |
| 11 | £76,000.00 | £149,335.29 |
| 12 | £82,000.00 | £171,255.43 |
| 13 | £88,000.00 | £195,470.89 |
| 14 | £94,000.00 | £222,222.03 |
| 15 | £100,000.00 | £251,774.37 |
| 16 | £106,000.00 | £284,421.22 |
| 17 | £112,000.00 | £320,486.62 |
| 18 | £118,000.00 | £360,328.54 |
| 19 | £124,000.00 | £404,342.43 |
| 20 | £130,000.00 | £452,965.15 |
Past performance doesn't guarantee future returns. Fees, taxes, and timing all reduce real-world results. Estimates only — not financial advice.
How investment growth is projected
The projection compounds your starting amount and monthly contributions at the chosen annual return, month by month. The presets anchor to long-run history: broad US stock indexes have averaged roughly 10% per year nominal (about 7% real) over many decades, classic 60/40 portfolios nearer 8%, and conservative allocations around 5%. These are averages across long horizons — not promises, and not predictions for any particular decade.
Worked example
$10,000 starting plus $500/month for 20 years:
- At 10% nominal: roughly $450,000 — about $130,000 contributed, the rest growth
- At 8%: roughly $343,000
- At 5%: roughly $233,000
The spread between assumptions is the single biggest uncertainty in any long-term plan — always test your plan at a rate below the historical average.
Nominal vs real returns
A nominal projection counts currency units; a real (inflation-adjusted) projection counts purchasing power. At 2.5% inflation, $1,000,000 in 30 years buys what about $480,000 buys today. For retirement and other distant goals, the "today's money" toggle gives the more honest picture — and pairs the expected return down by the same inflation assumption.
What this model ignores
- Volatility and sequence risk — real portfolios don't grow in a straight line, and the order of good and bad years matters when you're withdrawing.
- Fees — a 1% annual fee consumes roughly a quarter of a portfolio's final value over 30 years versus a 0.1% index fund.
- Tax — use tax-sheltered accounts (401(k)/IRA, ISA, RRSP/TFSA, super) before taxable ones.
For regular-deposit savings at a bank rate, the savings calculator is the better tool; for one-off return on a single investment, see the ROI calculator.
Related calculators
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Frequently asked questions
What return should I assume for investments?
How much will $500 a month grow in 20 years?
Should I look at nominal or inflation-adjusted returns?
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