🚀 Investment Growth Calculator (UK)
See how your investment portfolio grows over time with regular contributions and compound returns.
UK investment growth inside a Stocks & Shares ISA is fully tax-free on dividends, interest, and capital gains. The 2026/27 S&S ISA allowance is £20,000. Historic UK equity returns (FTSE All-Share since 1900) have averaged approximately 5% real and 7-8% nominal, with material decade-to-decade variation.
A UK Stocks & Shares ISA is the most tax-efficient general-purpose investment account available to retail investors in the world for amounts under £20,000/year. Compared with a US taxable brokerage (which pays tax on dividends annually and capital gains on realisation), or many European equivalents (which may carry wealth-tax exposure), the UK S&S ISA is a sealed tax-free wrapper that holds whatever ETFs, funds, shares, or bonds you put in it.
Allowance: £20,000/year across all ISA types combined (Cash, S&S, Lifetime, Innovative Finance). The Junior ISA adds £9,000/year for under-18s. Allowances do not roll over — use it or lose it each tax year, which ends 5 April.
Investment options inside an S&S ISA: - UK and global equity index funds (typical OCF 0.05-0.30%) - Active managed funds (typical OCF 0.50-1.50%) - Individual shares (UK + most major international markets via your broker) - Investment trusts - ETFs (UCITS-compliant; most US-domiciled ETFs are not eligible for retail UK investors post-PRIIPs) - Bonds and gilts
Realistic return assumptions: - UK equities (FTSE All-Share, since 1900): ~5% real, ~7-8% nominal - Global equities (MSCI World, since 1970): ~6% real, ~9% nominal - UK gilts: ~1-2% real, ~4-5% nominal - 60/40 global blend: ~3-4% real, ~6% nominal
Cost drag (often underweighted): - Platform fee: 0.15-0.45% on most retail platforms - Fund OCF: 0.05-1.50% - Trading costs (active management): 0.10-0.50% - Cumulative 1% per year cost drag reduces a 40-year terminal balance by approximately 25%
The calculator outputs nominal terminal value, real terminal value (CPI-adjusted), total contributions vs growth, and year-by-year drawdown sustainability at a chosen withdrawal rate. For ISA rules, HMRC's ISA Manager Reference Manual and the gov.uk ISA pages are authoritative; the ONS CPI series is the standard inflation reference.
See how your investment portfolio grows over time with regular contributions and compound returns.
How fast will my investments grow?
The Rule of 72 gives a quick estimate: 72 ÷ annual return = years to double. At a 7% real return, money doubles roughly every 10 years. With a $500 monthly contribution and 7% real growth, a $10,000 starting balance grows to about $250,000 over 20 years and $830,000 over 35 years.
| Year | Portfolio Value | Total Invested | Total Gains |
|---|
How to use this calculator
Takes about 2 minutes.
- Enter your initial investment amount
- Add the annual contribution you plan to make on top
- Set the expected annual return — 7 percent is a common long-term equity assumption
- Pick the investment period in years
- Click Calculate to see your projected portfolio value, total contributions, and interest earned
Try these scenarios
Tap a scenario to load it into the calculator above.
Key concepts
Lump sum vs. drip-feed. A lump-sum invested at day one mathematically outperforms the same money drip-fed monthly, because more of it spends more time in the market. Vanguard research finds lump-sum wins roughly two-thirds of the time over a 10-year horizon. The downside: bigger short-term regret if the market drops the week after you invest.
Dollar-cost averaging. Spreading contributions monthly smooths your average purchase price and protects against bad timing. It's mathematically suboptimal but psychologically easier — and most people earn money monthly anyway.
Real vs. nominal growth. A 7% nominal return with 3% inflation is a 4% real return. The calculator can be run either way — for long-horizon planning, real returns give you a meaningful purchasing-power figure.
Sequence and volatility. Two portfolios with the same average return but different paths end up at different places because of how returns interact with contributions and withdrawals. Higher volatility erodes the compound average (the 'variance drain').
Costs compound too. A 1% annual fee on a 7% return is a 14% drag on your gross return. Over 30 years, the difference between a 0.1% index fund and a 1% active fund can be 20-25% of your final balance.
The three major index choices for UK investors (2026)
Most UK retail investors pick between three global benchmarks for the equity portion of their Stocks & Shares ISA or SIPP. Each tracks a different slice of the world, carries a different OCF on the LSE-listed UCITS ETFs that wrap it, and produces different long-term returns. Choosing well matters less than people think — within reason, they're all reasonable. Choosing badly (picking individual stocks or expensive active funds instead) matters a lot.
S&P 500 tracks the largest 500 US companies by free-float market cap. It is the dominant single-country equity index and represents roughly 70% of US market cap and approximately 30% of MSCI World by weight. Top holdings as of 2026 include Apple, Microsoft, Nvidia, Amazon, Alphabet, Meta, and Berkshire Hathaway — a heavy technology tilt unmatched anywhere else. For UK investors, this is bought through LSE-listed UCITS ETFs such as VUSA (Vanguard, distributing) or CSPX (iShares, accumulating); both run at 0.07% OCF. We have a dedicated S&P 500 ISA growth page with worked compound-growth examples in GBP.
FTSE 100 tracks the 100 largest companies listed on the London Stock Exchange by market cap. Top holdings include AstraZeneca, Shell, HSBC, Unilever, BP, GlaxoSmithKline, and Diageo — heavy in energy, financials, mining, and consumer staples; light in technology. The index is structurally dividend-heavy, with a 2026 trailing yield around 3.8% versus 1.4% for the S&P 500. Approximately 75% of FTSE 100 revenue is earned abroad in non-GBP currencies, so it acts more like a global value index priced in sterling than a pure UK economy bet. ISF (iShares Core, 0.07% OCF, distributing) and VUKE (Vanguard, 0.09% OCF) are the standard wrappers.
MSCI World tracks roughly 1,500 large- and mid-cap stocks across 23 developed-market countries. US weighting sits around 70%, Japan and the UK roughly 5% each, with the remainder split across Germany, France, Canada, Switzerland, Australia, and the rest of developed Europe and Asia-Pacific. It is the standard global-equity benchmark for institutional money and is often described as "one fund, done" for diversified equity exposure. SWDA (iShares Core MSCI World, 0.20% OCF, accumulating) is the most common UK retail wrapper; VHVG (Vanguard FTSE Developed World, 0.12%) is a cheaper near-equivalent that uses FTSE's slightly broader developed-market definition.
A common point of confusion: MSCI World does not include emerging markets — China, India, Brazil, Taiwan, South Korea, and similar. For those, you need an MSCI ACWI tracker (All Country World Index, ~88% developed + 12% emerging) or a FTSE All-World tracker such as VWRP (Vanguard, 0.22% OCF, accumulating). FTSE All-World is functionally the most popular "single ETF for the entire equity portfolio" choice on UK platforms, because it captures around 4,000 stocks spanning developed and emerging markets in one ticker.
All three benchmarks above are eligible for Stocks & Shares ISAs and SIPPs — the ETFs are UCITS-compliant and LSE-listed. US-domiciled ETFs such as the famous VOO or SPY are not eligible for UK retail investors under PRIIPs rules, which is why we list the LSE-listed VUSA/CSPX equivalents instead.
Historical real returns — 1990-2024 and the 50-year view
"Past performance is not a guide" is true. But ignoring 50-100 years of return data is also a mistake — it's the only empirical anchor you have when picking a planning rate. Three sources are commonly used: Damodaran (NYU Stern) for US data back to 1928, Barclays' annual Equity Gilt Study for UK data back to 1899, and MSCI itself for MSCI World back to 1970.
S&P 500. Long-run annualised real return (post-CPI, USD, with dividends reinvested) for the US large-cap market is approximately 7% real over the 1928-2024 window per Damodaran's dataset. The most recent 35-year window (1990-2024) ran hotter at around 8.0% real annualised, helped by the tech-led 2010s. The worst 30-year window since 1928 still returned a positive real number (~4%); the best (1942-1971) ran near 11% real.
FTSE 100 (and the FTSE All-Share before 1984). UK large-cap has been a meaningful underperformer over the recent decade. Long-run annualised real return on UK equities (Barclays Equity Gilt Study, 1899-2024, dividends reinvested) is around 5% real GBP. The 1990-2024 window is closer to 4% real, and the 2010-2024 sub-period was barely 2% real — what UK retail investors call "the lost decade", driven by the structural weight of energy, mining, and banks during a period when those sectors lagged US technology. The trailing FTSE 100 dividend yield (~3.8% in 2026) does most of the heavy lifting; price returns alone have been close to flat for many years.
MSCI World. The global developed-market benchmark has returned approximately 6% real USD annualised since its 1970 inception, dominated by the heavy US weighting. For a GBP investor, sterling-hedged returns track the underlying closely, while unhedged returns add or subtract whatever GBP/USD did over the period. Over 1990-2024, MSCI World averaged around 6.5-7% real USD.
Three uncomfortable conclusions follow from the data:
- The S&P 500 has dominated for three decades. A 1990 UK retail investor who put GBP into a sterling-hedged S&P 500 tracker ended up with substantially more money than one who picked the FTSE 100. Whether that pattern continues is the central question of the 2026 investing debate.
- The MSCI World is the diversified bet. It captures the US tech-heavy outperformance via its ~70% US weighting but adds a meaningful slug of developed-market diversification at a small additional cost (0.20% vs 0.07% OCF). For most UK retail investors, this is the "default" recommendation.
- The FTSE 100 alone is a high-conviction bet on UK mega-cap value. It is not a diversified portfolio and it is not "the UK market" — it is 100 mostly-multinational large-caps with a heavy commodity and financials tilt. It can still be a sensible component, especially for the income-focused, but as a single-fund choice it lacks diversification.
For planning purposes on this calculator, 6% real is a defensible single-number assumption for a globally diversified equity portfolio over a 20-30 year horizon. Drop it to 4-5% real if you want to stress-test downside, or push to 7% real if you're modelling a US-equity-heavy allocation and willing to assume the recent run continues.
The 2026 UK ETF landscape — tickers and OCFs
UK retail investors hold equity index exposure almost exclusively through LSE-listed UCITS ETFs. Below are the standard options for each major index, with current ongoing-charges figures (OCF) and accumulating vs distributing flavours. Accumulating funds reinvest dividends inside the fund; distributing funds pay cash quarterly. Inside an ISA or SIPP both are equivalent from a tax perspective — pick whichever simplifies your record-keeping.
| Index | Ticker | Issuer | OCF | Type |
|---|---|---|---|---|
| S&P 500 | VUSA | Vanguard | 0.07% | Distributing |
| VUAG | Vanguard | 0.07% | Accumulating | |
| CSPX | iShares | 0.07% | Accumulating | |
| SPXP | Invesco | 0.05% | Accumulating (synthetic) | |
| FTSE 100 | ISF | iShares Core | 0.07% | Distributing |
| VUKE | Vanguard | 0.09% | Distributing | |
| VUKG | Vanguard | 0.09% | Accumulating | |
| MSCI World | SWDA | iShares Core | 0.20% | Accumulating |
| VHVG | Vanguard (FTSE Dev World) | 0.12% | Accumulating | |
| HMWO | HSBC | 0.15% | Accumulating | |
| FTSE All-World (developed + emerging) | VWRP | Vanguard | 0.22% | Accumulating |
A few practical notes that matter for the calculator output:
- Fund-level OCF is only half the cost. The other half is the platform fee (covered in the platform section below). On a £50,000 SWDA position the OCF costs you £100/year; on most platforms the platform fee on the same position is £25-£75/year.
- OCF differences compound. The gap between 0.07% (VUSA) and 0.20% (SWDA) is 13 basis points. Over 30 years on a £100,000 position growing at 6% gross, net of OCF that's the difference between £563,079 (at 5.93% net) and £542,713 (at 5.80% net) — about £20,366 of compounded cost for a portfolio that started six figures.
- Synthetic vs physical replication. Most LSE ETFs are physical (they hold the underlying shares); a few cheaper ones — notably Invesco's SPXP — are synthetic, using total-return swaps with counterparty banks. Synthetic ETFs can be cheaper and slightly tax-advantaged for US-equity exposure (no US dividend withholding tax) but add counterparty risk most retail investors don't want to think about. For ISA holdings, physical is the simpler default.
- Currency hedging. Most LSE ETFs are unhedged — your S&P 500 returns reflect both US market performance and GBP/USD moves. GBP-hedged share classes exist (e.g. GSPX for iShares' S&P 500) at slightly higher OCF (~0.10%). For 25+ year horizons, currency hedging usually adds cost without improving risk-adjusted returns. Don't bother unless you need GBP cash within five years.
Wrapper choice — ISA vs SIPP vs GIA over 30 years
Once you've picked your index and ETF, the second-largest decision is the tax wrapper. Most UK investors should max the ISA first, then the SIPP, and only use a General Investment Account (GIA) once both are full. To make this concrete: assume you invest £20,000/year for 30 years at 6% real annualised under each wrapper, with end-of-year contribution timing matching the calculator above.
| Wrapper | Gross terminal value | Tax on withdrawal | Net to investor |
|---|---|---|---|
| Stocks & Shares ISA | £1,581,164 | £0 | £1,581,164 |
| SIPP (basic-rate relief, basic-rate retiree) | £1,976,455 | £296,468 | £1,679,987 |
| General Investment Account (~0.5%/y tax drag) | £1,448,710 | already deducted | £1,448,710 |
The SIPP wins on paper. The 20% basic-rate tax relief on the way in grosses up your £20,000/year contribution to £25,000/year, lifting the gross terminal value to £1,976,455. On withdrawal, 25% comes out tax-free (the pension commencement lump sum) and the remaining 75% is taxed at your marginal rate — assumed 20% for a basic-rate retiree below the £50,270 income threshold. That yields a net of £1,679,987, roughly £100,000 ahead of the ISA. For a higher-rate taxpayer making contributions and a basic-rate retiree on the way out (the textbook SIPP tax arbitrage), the advantage is much larger.
The ISA wins on flexibility. You can withdraw from an ISA at any age without penalty; the SIPP locks money up until age 57 (rising from 55 in April 2028). For investors under 40 with a long time horizon, the SIPP tax advantage is mathematically real but practically irrelevant if you might want the money before 57. Most UK retail investors should max the ISA first.
The GIA loses on tax drag. The 0.5%/year drag in the table is a rough composite of dividend tax (8.75% basic / 33.75% higher on dividends above the £500 allowance from April 2024), capital gains tax (currently 18% basic / 24% higher on gains above the £3,000 annual exempt amount from April 2024), and the fact that even index funds turn over some holdings each year, triggering CGT events. The exact drag depends on portfolio yield, your tax band, and how often you rebalance — 0.5% is a workable average for a buy-and-hold global tracker.
The optimal stack for most UK retail investors is straightforward:
- Max the £20,000 ISA each tax year
- Once the ISA is full, contribute to the SIPP up to the £60,000 annual allowance (or your earned income, whichever is lower)
- Only use a GIA if both wrappers are full or if you need pre-57 liquidity above what the ISA covers
- If you're a higher-rate taxpayer, the SIPP often wins over the ISA on net-of-tax terms, especially if you'll be a basic-rate taxpayer in retirement
Whichever wrapper you use, the underlying ETF holdings can be identical — the same VWRP or SWDA inside an ISA, SIPP, and GIA produces three radically different net outcomes solely because of the wrapper.
The compound-growth maths — worked examples
The headline number from any growth calculator is dominated by three inputs: how much you start with, how much you add each year, and the rate you assume. Tweaking any of them by a percentage point or two changes terminal values by surprising amounts. The table below holds the start (£10,000) and contributions (£500/month, i.e. £6,000/year) constant, and varies only the rate and the horizon — all figures use end-of-year contribution timing to match the calculator above exactly.
| Horizon | Total contributions | At 4% real | At 6% real | At 8% real |
|---|---|---|---|---|
| 10 years | £70,000 | £86,839 | £96,993 | £108,509 |
| 15 years | £100,000 | £138,151 | £163,621 | £194,634 |
| 20 years | £130,000 | £200,580 | £252,785 | £321,181 |
| 25 years | £160,000 | £276,534 | £372,106 | £507,120 |
| 30 years | £190,000 | £368,944 | £531,784 | £780,326 |
| 35 years | £220,000 | £481,374 | £745,470 | £1,181,754 |
Three observations that most people get wrong on first read:
The rate matters more than people think, especially over long horizons. At a 25-year horizon, 6% versus 8% is a £135,014 swing — £372,106 versus £507,120 — on £160,000 of contributions. By year 35, the gap widens to £436,284 (£745,470 vs £1,181,754). Picking an 8% planning rate when you'll actually realise 6% is not a small error.
Contributions dominate early years, returns dominate late years. At year 10 with a 6% rate, you've contributed £70,000 and your portfolio is £96,993 — only £26,993 of growth. By year 30 with the same rate, contributions have risen to £190,000 but the portfolio is £531,784 — growth of £341,784 is now ~1.8× total contributions. The "ramp" starts being visible around year 15.
An extra five years at the back end is worth more than five extra years at the front. Going from year 25 to year 30 at 6% adds £159,678 (£372,106 → £531,784). Going from year 5 to year 10 at the same rate adds only £49,788. This is mathematically why "start early" advice is so insistent and why the worst time to start is never — even a delayed start is still worth more than not starting.
For lump-sum investing without contributions, the maths is simpler: £10,000 at 6% real over 30 years = £57,435; at 7% real = £76,123; at 8% real = £100,627. Each one-percentage-point increment is roughly +33% to the terminal value over 30 years — a sharper sensitivity than most people intuit.
Inflation-adjusted scenarios — nominal vs real
Most retail calculators output nominal pounds — the headline number in future money, before inflation. That's useful for short horizons but actively misleading for retirement planning. A £500,000 nominal pot in 2056 sounds enormous; deflated by 30 years of 2.5% UK CPI it's the equivalent of £238,371 in today's money. The same £500k in today's purchasing power requires you to actually hit £1,048,784 nominal by 2056. Conflating the two is the single most common planning error.
The cleanest fix is to plan in real returns — the return after subtracting inflation — so the terminal number is already in today's pounds. The relationship is multiplicative: (1 + real) = (1 + nominal) / (1 + inflation).
| Nominal return | Inflation assumption | Real return | What it represents |
|---|---|---|---|
| 8.0% | 3.0% | 4.85% | Bullish equity assumption, mild inflation |
| 7.0% | 2.5% | 4.39% | Standard balanced-portfolio plan with UK 20-year CPI average |
| 5.0% | 3.0% | 1.94% | Conservative 60/40 blend, sticky inflation |
| 9.5% | 2.5% | 6.83% | Long-run S&P 500 nominal less long-run UK CPI |
| 4.0% | 5.0% | -0.95% | 2022-2023 stress case (high inflation, lagging returns) |
The UK CPI 20-year average is ~2.5% (ONS series, 2005-2024 inclusive). The 50-year average is closer to 4% but heavily skewed by the 1970s; the BoE's modern inflation target is 2%, and outside the 2022-23 spike most years since the GFC ran below it. For a long-horizon plan, 2.5-3.0% inflation is the sensible base case.
If you input nominal returns into the calculator and want to read the output in real terms, divide the terminal value by (1 + inflation)^years. At 2.5% inflation over 30 years, that's a divisor of 2.098 — so a nominal £1,000,000 pot is worth £476,743 in today's pounds. Alternatively, just input the real return directly (e.g. 4.5% real instead of 7% nominal) and the calculator's output is already in today's pounds.
For a deeper treatment, see our UK inflation impact calculator, which lets you input a starting purchasing power and see how it erodes over decades at various CPI assumptions.
Platform fee impact — picking the cheapest ISA platform for your pot size
Beyond fund OCFs, you pay an annual platform fee to whoever holds your ISA. The structure varies wildly across the major UK retail platforms, and the cheapest choice changes with portfolio size. Below is a snapshot of the three most common 2026 options for a Stocks & Shares ISA:
- Vanguard Investor — 0.15% of holdings per year, capped at £375 (i.e. flat fee above £250,000). Fund range limited to Vanguard's own products.
- Trading 212 ISA — 0% platform fee, no FX fee, free trading on UK and US shares and most major ETFs. Funded by securities lending and interest on uninvested cash.
- Interactive Investor — flat £4.99/month (£59.88/year) on the Investor Essentials plan, or £11.99/month on the Investor plan (which includes the SIPP and a regular-investment service). Open architecture (any LSE-listed fund or ETF).
| Portfolio size | Vanguard 0.15% | Trading 212 | Interactive Investor £4.99/mo | Cheapest |
|---|---|---|---|---|
| £10,000 | £15.00 (0.150%) | £0.00 (0.000%) | £59.88 (0.599%) | Trading 212 |
| £50,000 | £75.00 (0.150%) | £0.00 (0.000%) | £59.88 (0.120%) | Trading 212 |
| £100,000 | £150.00 (0.150%) | £0.00 (0.000%) | £59.88 (0.060%) | Trading 212 |
| £250,000 | £375.00 (0.150%) | £0.00 (0.000%) | £59.88 (0.024%) | Trading 212 |
| £500,000 | £375.00 (0.075%) | £0.00 (0.000%) | £59.88 (0.012%) | Trading 212 |
Trading 212 is mathematically the cheapest at every portfolio size we modelled — the headline platform fee is zero. The catch is that the platform is younger than Vanguard or II, has a narrower product range (no SIPP at scale, limited fund universe versus full open-architecture), and revenue comes from securities-lending and FX spreads that the user doesn't see directly. Investors with seven-figure ISA pots often prefer a paid platform for the institutional governance, even at the cost of an extra £60-£375/year.
The two breakeven points worth knowing:
- Vanguard becomes cheaper than Interactive Investor at portfolios below ~£40,000 (0.15% of £40k = £60, matching II's £59.88/year).
- The Vanguard cap kicks in at £250,000 — above that, your 0.15% effectively starts falling. By £500,000 the effective rate is 0.075%; by £1,000,000 it's 0.0375%.
The practical advice for most UK investors: if you're below £40,000, Trading 212 or Vanguard work equally well. Between £40,000 and £250,000, Interactive Investor's flat fee starts to look attractive once you'd otherwise pay >£60 on a percentage platform. Above £250,000, the Vanguard cap and II flat fee converge in cost — pick on product range, not headline price. Above £1,000,000, almost everything looks cheap; focus on service quality, tax-reporting tools, and whether the platform supports the funds you actually want to hold.
Platform-fee drag compounds. A 0.45% all-in cost (e.g. 0.15% Vanguard + 0.20% SWDA + 0.10% miscellaneous) on a £100,000 portfolio at 6% gross over 30 years compounds to £505,530 (at 5.55% net). The same portfolio with a leaner 0.15% all-in setup (5.85% net) compounds to £550,460 — a £44,930 gap that represents pure cost drag. Over a working life, the platform choice is worth genuine money.
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