ISA Calculator

Calculate how your tax-free ISA savings could grow over time with lump sum or regular deposits.

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ISA Growth Projection

Total Contributions
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Final Balance
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Total Interest / Growth
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Effective Annual Return
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This is a projection based on assumed growth. Past performance is not a guide to future returns. ISA allowances may change each tax year.

UK ISA Calculator — How to Use It

Enter a lump sum deposit, regular monthly contribution, your expected annual interest or growth rate, and the number of years. The calculator projects your total ISA pot, total tax-free growth, and effective return. All figures are estimates — actual returns depend on market performance and the rate you receive.

ISA Allowance 2025/26

The annual ISA allowance is £20,000 per person for the 2025/26 tax year (6 April 2025 – 5 April 2026). You can split this across multiple ISA types in the same year, but your total contributions across all ISAs cannot exceed £20,000. Any unused allowance is lost at the end of the tax year — it does not carry forward.

Types of ISA Available in the UK

  • Cash ISA: Works like a savings account — deposits earn tax-free interest. Very low risk. Best rates currently 4–5% (fixed-rate options). FSCS protected up to £85,000 per institution.
  • Stocks & Shares ISA: Invests in funds, shares, and bonds within a tax-free wrapper. Higher long-term growth potential but your capital is at risk. Historically, global index funds have returned around 7–10%/year before inflation over the long term.
  • Innovative Finance ISA (IFISA): Invests in peer-to-peer lending. Higher potential returns but higher risk — NOT covered by the FSCS.
  • Lifetime ISA (LISA): For first-time buyers and retirement. You can save up to £4,000/year and receive a 25% government bonus (up to £1,000/year). Must be used to buy your first home (up to £450,000) or accessed at age 60+. There is a 25% withdrawal penalty for other uses (which takes back more than the bonus).
  • Junior ISA (JISA): Tax-free savings for under-18s. Allowance of £9,000/year for 2025/26. The child can access funds at 18.

Cash ISA vs Stocks & Shares ISA — Which Is Right for You?

Choose a Cash ISA if you need the money within 1–5 years or cannot afford to lose any capital. Choose a Stocks & Shares ISA if you are investing for 5+ years and can accept short-term falls in value. Over long time horizons, stocks have historically outperformed cash, but this is not guaranteed. Many investors use both — cash for short-term goals and S&S ISA for long-term wealth building.

Should I Use My ISA Allowance First or Pension First?

For most people: max your employer pension match first (it is essentially free money), then use the ISA for flexibility. Pensions give upfront tax relief and employer contributions, but you cannot access them until age 57 (rising to 57 in 2028). ISAs are accessible at any time and have no lifetime limit, making them ideal for medium-term goals like home deposits or financial independence.

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