Free UK tool · Investment calculator UK
Project your portfolio forward with realistic UK assumptions — ISA tax-free wrapper, inflation-adjusted real returns, compound growth from monthly contributions. Free, private, no sign up. Nothing you enter ever leaves your device.
Your data never leaves your device. Ever.How to use
The investment calculator UK above runs the maths the moment you start typing. Here's how to get a useful number out of it.
Toggle between Stocks & Shares ISA and General Investment Account to see how the tax wrapper affects your end result. Use ISA first — the £20,000 annual allowance is generous enough that most UK investors never need a GIA.
Understanding investment returns
Investing feels mysterious until you understand the levers. There are really only four.
Returns earned not just on your original deposit but on the returns themselves, compounding indefinitely. £10,000 at 7% over 30 years becomes ~£76,000 — about 7.6× your starting money — without you adding a single pound. The same £10,000 with monthly contributions of £200 becomes ~£325,000. Compounding's gift is non-linear: doubling the time horizon often more than triples the final pot.
Two investors, both with £200/month at 7%. Investor A starts at 25, stops at 35 (10 years × £200 = £24,000 contributed). Investor B starts at 35, invests until 65 (30 years × £200 = £72,000 contributed). At 65, Investor A has roughly £200,000; Investor B has roughly £244,000. Investor A contributed a third of what B did and ended up almost level. The 30s and 40s aren't catch-up time — they're prime time, and starting them at zero is expensive.
"Nominal" is the number on your statement. "Real" is the same number after inflation. If your portfolio earns 7% nominal but inflation runs at 2.5%, your real return is ~4.4%. Long-term planning should always be in real terms because the real number is what your money will actually buy. The calculator's inflation field translates the nominal final value into today's pounds for that reason.
Long-run averages (real, after inflation): UK equities ~5%, US equities ~6%, global equities ~5%, UK gilts ~1–2%, corporate bonds ~2–3%, cash 0–1%, residential property ~2–3%. A balanced 60/40 portfolio of global equities and high-quality bonds has averaged ~4–5% real long-run. Use those as planning baselines; anything above 7% nominal projected over a 20-year horizon should be questioned.
A 1% annual fee feels small. Over 30 years on a £100,000 portfolio it's the difference between ~£762,000 (no fee, 7% return) and ~£574,000 (1% fee, 6% net return) — about £188,000 of forgone wealth. UK index trackers from Vanguard, iShares, etc. typically charge 0.10–0.25%. Active funds often 0.7–1.5%. Fees compound against you the same way returns compound for you.
UK specifics
Every UK adult has a £20,000 annual ISA allowance across all ISA types — Cash, Stocks & Shares, Lifetime (capped at £4,000), and Innovative Finance. Allowances reset on 6 April every tax year, and unused allowance doesn't carry over. Inside an ISA, no income tax on dividends, no capital gains tax on growth, no tax on withdrawals at any age. For most UK investors, a stocks and shares ISA calculator is the right tool — the assumption being that you'll invest inside the wrapper.
Outside the ISA wrapper, gains and dividends are taxed. The annual CGT exemption is £3,000 for 2025/26 (down from £6,000 the year before, and £12,300 before that). Above that, gains are taxed at 18% (basic rate) or 24% (higher rate) for residential property and shares. The annual dividend allowance is £500, with dividend income above that taxed at 8.75% basic / 33.75% higher / 39.35% additional. The toggle in the calculator above models a simplified version of this drag.
If you're investing for retirement, a SIPP (Self-Invested Personal Pension) gives you tax relief at your marginal rate on contributions. A basic-rate taxpayer's £80 becomes £100 inside the pension; a higher-rate taxpayer can claim back another £20 via self-assessment, so £100 in pension only costs £60 of take-home pay. The trade-off: locked away until 57 (rising to 58 in 2028). For most UK investors, the optimal stack is: workplace pension to capture employer match → ISA → SIPP for additional retirement-specific savings.
The investments held inside can be identical — funds, shares, ETFs. The difference is the wrapper. Use the ISA first. A GIA is only worth opening once you've filled the £20,000 ISA allowance for the year, or for goals where you want flexibility outside ISA rules. The calculator's account-type toggle shows the tax drag a GIA introduces — typically 10–20% less wealth at the end versus an ISA holding the same investments.
In a GIA, you're potentially taxed on dividends every year (above the £500 allowance), even if you reinvest them. CGT is only triggered when you sell. "Reporting funds" pass dividends through transparently for UK tax purposes; "non-reporting" funds get punished with income tax on the entire gain at your marginal rate. Stick to UK reporting funds (most major ETFs and OEICs are) to avoid that trap. The calculator above assumes reporting status.
FAQ
The questions people most often type into Google about UK investing.
It depends on amount, return rate, and time. Quick benchmarks: £200/month at 7% becomes ~£104,000 over 20 years and ~£244,000 over 30 years. The same £200/month at 5% becomes ~£82,000 over 20 years.
The free UK investment calculator above lets you plug in your exact numbers to see your projected portfolio.
Standard compound growth formula: FV = PV × (1+r)n + PMT × ((1+r)n − 1) / r, where PV is your starting lump sum, PMT is your monthly contribution, r is the monthly return rate, and n is the number of months.
The calculator compounds monthly and shows your projected portfolio in nominal pounds plus an inflation-adjusted figure that translates the result into today's purchasing power.
A Stocks & Shares ISA is a tax-free wrapper for investments — no income tax on dividends, no capital gains tax on growth, no tax on withdrawals at any age.
A stocks and shares ISA calculator uses the same compound formula as a normal investment calculator but shows you the full projection without any tax drag. The calculator on this page lets you toggle between ISA (full tax-free growth) and a General Investment Account.
Enter your starting amount, monthly contribution, expected annual return, and number of years. The calculator compounds monthly using the standard formula.
The year-by-year table shows how growth gradually overtakes contributions — usually around year 8–10 at 7% returns, the "compound interest crossover" point that's emotionally significant.
A common UK rule of thumb: aim for at least 15% of gross salary across pension and ISA combined. On a £40,000 salary that's roughly £500/month.
Auto-enrolment via your workplace pension covers part of this (5% employee + 3% employer), so additional ISA contributions of 5–10% of salary are typical for someone on track. The calculator above helps you back-solve from a target.
For long-run planning, the historical UK / global equity average is roughly 7% nominal per year (about 4–5% real after inflation). Bonds have averaged 3–4%. A balanced 60/40 portfolio tends to land around 5–6% nominal long-run.
Don't model 9–10% — that's been an exceptional decade, not a baseline. 5–7% is the conservative-to-realistic range for UK investors with a long horizon.
The investments held inside can be identical. The wrapper differs. A Stocks & Shares ISA grows tax-free: no dividend tax, no CGT, no withdrawal tax.
A General Investment Account has no wrapper — dividends are taxed above the £500 allowance, and gains are taxed above the £3,000 CGT exemption. UK investors should fill their £20,000 ISA allowance before using a GIA.
Inflation reduces the real purchasing power of your portfolio. £100,000 today buys what £67,000 buys in 20 years at 2% inflation, or what £55,000 buys at 3% inflation.
Your nominal return needs to beat inflation to grow your wealth in real terms. The calculator above shows both nominal (raw) and inflation-adjusted (real, in today's pounds) figures.
The full picture
Vault is the home for everything this calculator hints at — your investments, ISAs, pensions, savings, and how it all fits together as a single net-worth view. Same principles: free, private, local only. Nothing you enter ever leaves your device.
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