ISA Savings Calculator
See how an ISA could grow from a starting balance and monthly deposits, with deposits capped at the annual ISA allowance.
The ISA allowance is £20,000 for the 2026 to 2027 tax year, shared across all your ISAs (GOV.UK, checked 19 October 2026). Growth inside an ISA is free of UK income tax and capital gains tax.
Example: £5,000 to start plus £500 a month (£6,000 a year, inside the allowance) at an assumed 4% for 10 years grows to about £81,079.07, of which £16,079.07 is tax-free interest. The 4% is an illustration, not a current ISA rate.
Compare with the compound interest calculator or plan a home deposit alongside the UK stamp duty calculator.
Build your scenario
Use your actual figures where available. The output is an educational estimate based on the assumptions below.
Displayed amounts are rounded to two decimal places. Keep the same currency and time period across related inputs.
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ISA allowance (GOV.UK)
- In the 2026 to 2027 tax year (6 April 2026 to 5 April 2027), you can save up to £20,000 in ISAs in total, split across cash, stocks and shares, innovative finance and Lifetime ISAs.
- A Lifetime ISA takes up to £4,000 of that allowance.
- From 6 April 2027, the government has legislated a £12,000 cash ISA limit for people aged 64 or under, within the same £20,000 overall limit. Savers aged 65 and over keep a £20,000 cash ISA limit.
Deposits per year = min(monthly × 12, allowance)
Worked example: £500 a month for 10 years
Starting with £5,000 and saving £500 a month (£6,000 a year, well within the allowance) at an assumed 4% for 10 years gives about £81,079.07: £60,000 of deposits and £16,079.07 of tax-free interest. The 4% rate is an illustration, not a current ISA rate.
Why the wrapper matters
Interest, dividends and gains inside an ISA are free of UK income tax and capital gains tax, and you don't need to report them. Outside an ISA, savings interest above your personal savings allowance is taxable. The allowance resets each tax year and unused allowance does not carry forward.
Sources
- GOV.UK: Individual Savings Accounts: 2026 to 2027 allowance
- GOV.UK: Cash ISA limit reduction from 6 April 2027
Related calculators
- Savings goal calculator: monthly amount to hit a target
- Compound interest calculator: growth with different compounding
- Mortgage affordability (US): price from income with the 28/36 rule
- 401(k) calculator: retirement balance with an employer match
Dated figures on this page are tracked in the figures update log.
Frequently asked questions
What is the ISA allowance for 2026 to 2027?
£20,000 in total across all your ISAs for the tax year from 6 April 2026 to 5 April 2027.
Is the cash ISA limit changing?
Yes. From 6 April 2027, people aged 64 or under can put up to £12,000 a year into cash ISAs, within the £20,000 overall limit. Those aged 65 and over keep £20,000.
Does unused allowance carry forward?
No. The ISA allowance resets each tax year.
Is ISA interest taxed?
No. Interest and gains inside an ISA are free of UK income tax and capital gains tax.
What is the ISA allowance for 2026/27?
£20,000 for the 2026 to 2027 tax year, according to GOV.UK. It is the total you can pay into all your ISAs in that tax year.
How much will £500 a month in an ISA grow to?
Starting with £5,000 and adding £500 a month at an assumed 4% for 10 years, about £81,079.07. Actual returns depend on the ISA and can differ.
Worked example: what could £10,000 in an ISA grow to?
At an assumed 5% a year for 10 years, £10,000 grows to about £16,288.95, with no UK tax on the growth. You can pay in up to £20,000 a year across all ISAs in 2026–27.
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