ISA Savings Calculator
Every UK adult gets a £20,000 ISA allowance each tax year, and everything inside an ISA grows free of income tax and capital gains tax. This calculator shows how your ISA could grow.
How to use this calculator
- Enter current ISA balance.
- Enter monthly contribution.
- Enter expected annual return.
- Enter time horizon.
- Your results appear instantly below and update as you change the numbers.
How this calculator works
Interest and investment growth compound monthly on your balance: each month you earn one-twelfth of the annual return on everything accumulated so far, and your monthly contribution is added on top. The chart shows your balance year by year, splitting contributions from growth. Worked example: a £10,000 ISA topped up with £200 a month at 5% reaches about £47,530 in 10 years — £34,000 of contributions and £13,530 of tax-free growth. You can contribute up to £20,000 per tax year across all your ISAs, split between cash, stocks & shares, and (up to £4,000) a Lifetime ISA.
Frequently asked questions
How much can I put in an ISA in 2026/27?
£20,000 across all ISAs in the tax year, with no more than £4,000 of that in a Lifetime ISA. The allowance resets every 6 April — it's use-it-or-lose-it. From April 2027 the cash ISA allowance is set to drop to £12,000 for under-65s, so 2026/27 is the last full year of £20,000.
Cash ISA or stocks & shares ISA?
Cash ISAs pay interest (typically 3–5% in 2026) with no risk to your capital. Stocks & shares ISAs have historically returned more over long horizons (averaging 6–9% a year) but can fall short-term. Many people hold a cash ISA for short-term goals and a stocks & shares ISA for retirement and 5+ year goals.
Is ISA growth really tax-free?
Yes — no income tax on interest or dividends and no capital gains tax on sales, with no reporting on your tax return. That's especially valuable now: outside an ISA, your personal savings allowance only shields the first £1,000 (basic rate) or £500 (higher rate) of interest a year.
Disclaimer: Results are estimates for general information only and do not constitute financial, tax, or legal advice. Figures reflect the current tax year and may change. Always confirm current limits and consult a qualified professional before making decisions. Official figures: GOV.UK income tax rates · National Insurance · Stamp Duty Land Tax.