Monthly Investment Calculator — UK
See how a monthly investment grows over time at UK's historical returns. No signup, no account needed.
Enter a monthly amount, a return rate between 0% and 100%, and a duration above zero (up to 50 years) to see results.
Where to invest in UK
ISA allowance £20k/year tax-free. Providers: Vanguard, Hargreaves Lansdown, AJ Bell. FTSE 100 historical ≈ 7%.
Returns are long-term historical averages, not guarantees - markets fall as well as rise. Invest for the long term and diversify.
The power of compounding
Investing £400 per month for 15 years at 7% p.a.:
- Future value: £127,524
- Total invested: £72,000
- Estimated gains: £55,524
That is roughly 1.8× your money - most of it from compounding. Scale the £400 to your own monthly amount, and remember that starting earlier matters more than investing more.
How to start - and stay - invested in UK
- Automate a fixed monthly amount so you invest through good months and bad.
- Start small; you can raise the amount as your income grows.
- Favour low-cost, diversified funds over picking individual stocks.
- Stay invested through market dips - time in the market beats timing the market.
A real-data rate check: long-term returns in the UK (2026)
Many UK SIP and regular-investment calculators default to 9–10% a year, a figure borrowed from long-run US stock market averages. UK equities have historically delivered lower returns. According to the Barclays Equity Gilt Study, UK shares produced an average annual real (inflation-adjusted) return of around 5.1% over the 114 years to the study's dataset. More recently, IG's analysis of the FTSE 100 found a 20-year annualised total return (including reinvested dividends) of about 6.4% for the period to 2026 (IG.com, published 15 April 2026) — below the S&P 500's long-run average over the same stretch.
Adding back long-run UK inflation, a nominal return in the 6–8% a year range is a more evidence-based assumption for a diversified UK equity portfolio than 9%. The Office for National Statistics reported UK CPI inflation of 3.1% in the 12 months to August 2026 (ONS, published 16 September 2026), a reminder that inflation itself erodes real purchasing power.
A more realistic example: investing £300 per month at a 7% assumed annual return would grow to roughly £95,640 after 15 years (from £54,000 contributed) and around £157,190 after 20 years (from £72,000 contributed).
Frequently Asked Questions
How does a monthly investment work in UK?
You invest a fixed amount each month into funds or an index. You buy more units when prices are low and fewer when high (cost averaging), and returns compound over time.
What return can I expect in UK?
Long-term historical equity returns are around 7% per year here, though any single year can be sharply up or down. ISA allowance £20k/year tax-free. Providers: Vanguard, Hargreaves Lansdown, AJ Bell. FTSE 100 historical ≈ 7%.
How much do I need to start investing in UK?
Most platforms let you start small and increase later. Setting up an automatic monthly investment builds discipline and smooths out market timing.
Should I invest a lump sum or monthly in UK?
Investing monthly spreads your entry across market ups and downs (cost averaging) and is easier to budget. A lump sum can do better in a steadily rising market but carries more timing risk.
Is investing better than a fixed deposit in UK?
Investing targets higher long-term growth but carries market risk; fixed deposits are safer but usually return less. Many people hold both, matched to their time horizon.
Are investment gains taxed in UK?
In the UK, capital gains above your annual Capital Gains Tax allowance are taxable via HMRC; using a Stocks & Shares ISA (annual allowance £20,000 for the 2026/27 tax year) shelters both gains and dividends from tax entirely.
Is 9% a realistic annual return assumption for a UK SIP?
It is on the optimistic side for UK equities specifically. Long-run studies such as the Barclays Equity Gilt Study put UK equities' real (inflation-adjusted) return at roughly 5.1% a year over more than a century, and a recent 20-year FTSE 100 study found a 6.4% annualised nominal total return to 2026. Adding UK inflation back in, a 6-8% nominal assumption is better supported by the data than 9%.
Where does the 7% rate on this calculator come from?
It reflects a blend of long-run UK equity return data: the Barclays Equity Gilt Study's ~5.1% real return figure plus an allowance for long-term inflation, and a 20-year FTSE 100 annualised total return of about 6.4% (IG.com, 2026).
Does this calculator account for inflation or investment fees?
No. The projection is a gross, before-fees, before-tax, nominal figure. UK CPI inflation was 3.1% in the 12 months to August 2026 (ONS), so the real (inflation-adjusted) value of your future pot will be lower than the headline number shown.
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Sources
Return assumptions and rates are compiled from each country's central-bank publications, recognized market-index data and the typical offerings of major providers, reviewed for 2026 and subject to change. Returns are long-term historical averages, not guarantees. See our methodology and editorial policy for how we source and update this data.
Additional sources for this page
Barclays Equity Gilt Study, UK equity real return data cited via Wingate Financial Planning: Investing Lessons From 114 Years Of Data. FTSE 100 20-year annualised total return (IG.com, 15 April 2026): What are the average returns of the FTSE 100?. UK CPI inflation, 12 months to August 2026 (ONS, published 16 September 2026): Consumer price inflation, UK: August 2026. See our methodology and editorial policy for how we source and update this data.