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Investment Calculator (UK)

£
yr
%

Total value

£104,793

Expected return: 7%
Amount invested
£48,000
Estimated returns
£56,793
Total value
£104,793

Growth over time

120
Amount investedEstimated returns

Estimates only. Returns are not guaranteed; past performance does not predict future results.

How this investment calculator works

This free UK investment calculator projects how your money could grow in funds (OEICs, unit trusts), index funds and ETFs. Pay in monthly, invest a lump sum, or both; pick an expected growth rate and a time horizon, and it compounds your money month by month. Crucially it shows growth net of fees and tax across a Stocks & Shares ISA, a SIPP and a General Investment Account — and can adjust for inflation to show today's money.

Using each mode

  • Monthly: enter a regular monthly contribution (from as little as £25). The calculator adds and compounds each payment.
  • Lump sum: model a single investment growing over time.
  • Step-up: raise your monthly amount by a set percentage each year to keep pace with rising earnings or inflation.
  • Withdrawal: draw a regular income from a pot and see how long it lasts (useful for pension drawdown planning).
  • Goal: set a target and solve for the monthly amount, lump sum, time or return required.

Toggle inflation-adjusted, fees, after-tax and the scenario range to stress-test the plan.

What growth rate should I use?

Global equities have returned roughly 7–9% a year on average over the long run before inflation; a diversified fund is commonly modeled at 5–7% after charges. The FCA requires providers to use standardised projection rates, but real returns are never guaranteed and vary year to year. The calculator defaults to 7% and offers a conservative/expected/aggressive band so you see a realistic spread.

How fund returns are taxed in the UK

Inside a Stocks & Shares ISA (£20,000 annual allowance for 2025/26) all growth, dividends and withdrawals are completely tax-free. In a SIPP/pension, contributions get tax relief and 25% can usually be taken tax-free at retirement, with the rest taxed as income. In a General Investment Account, capital gains above the £3,000 annual exempt amount are taxed at 18% or 24% (2025/26), and dividends above the £500 allowance are taxed at 8.75%/33.75%/39.35%. See GOV.UK guidance on Capital Gains Tax and ISAs for the official figures.

How fund charges reduce returns

The ongoing charges figure (OCF/TER) is deducted from your fund every year and compounds against you. Over decades, paying 1.0% instead of 0.15% can cost tens of thousands of pounds on a meaningful pot. Platform fees add to this. Use the fees toggle to see your net-of-charges result — tracker funds and ETFs typically charge 0.05%–0.25%.

ISAs, SIPPs and the order to use them

For most people the priority is: capture any workplace pension match, then use a Stocks & Shares ISA for flexible tax-free growth, and a SIPP for long-term retirement money with up-front tax relief. The £20,000 ISA allowance resets each tax year and cannot be carried forward. Switch the account type in the tax toggle to compare the same fund inside an ISA versus a taxable GIA.

Is a Stocks and Shares ISA really tax-free?⌄
Yes. Within the £20,000 annual ISA allowance, all capital gains, dividends and withdrawals from a Stocks & Shares ISA are free of UK tax, and you do not even report them on a tax return. This is why an ISA almost always beats a General Investment Account for long-term fund investing.
What return should I assume for a UK investment calculator?⌄
A diversified global equity fund is commonly modeled at around 5–7% a year after charges, based on long-run averages of roughly 7–9% before inflation. Returns are not guaranteed; use the conservative/expected/aggressive scenario band to see a realistic range rather than relying on a single figure.
How is capital gains tax charged on funds outside an ISA?⌄
In a General Investment Account, gains above the annual exempt amount (£3,000 for 2025/26) are taxed at 18% (basic-rate band) or 24% (higher/additional). Dividends above the £500 dividend allowance are taxed at 8.75%, 33.75% or 39.35%. Inside an ISA or pension these taxes do not apply.
How much do I need to invest each month to reach £100,000?⌄
Use Goal mode, set the target to £100,000 and solve for the required monthly investment. As a rough guide, at 7% growth investing around £190 a month for 20 years reaches about £100,000. The exact figure depends on your time horizon and assumed return.
Can I use this as a SIPP or pension calculator?⌄
Yes. Select the SIPP account type, use Monthly or Lump sum mode for the accumulation phase, and Withdrawal mode to model drawdown — entering your pot and a monthly income to see how many years it lasts at your assumed growth rate.
What is the difference between an OEIC, a unit trust and an ETF?⌄
OEICs and unit trusts are open-ended UK funds priced once a day; ETFs are exchange-traded funds you buy and sell like shares throughout the day, usually with very low charges. The maths of returns is the same — this calculator works for all of them; only the fees differ.