ISA Calculator guide
ISA Calculator: Tax-Free Savings and Investments
Use our ISA calculator to project how a cash, stocks and shares or Lifetime ISA could grow, with the £20,000 allowance and the Lifetime ISA bonus.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
An ISA (individual savings account) lets you save or invest without paying tax on the interest, dividends or gains. It's the UK's nearest equivalent to a US Roth IRA. Our ISA Calculator projects how yours could grow.
How to use the calculator (ISA Calculator)
- Choose the ISA type: cash, stocks and shares, or Lifetime.
- Enter a starting amount and monthly contribution.
- Enter the expected growth and number of years.
ISA allowances for 2026/27
| ISA | Limit |
|---|---|
| All ISAs combined | £20,000 a year |
| Lifetime ISA | £4,000 a year (counts towards the £20,000) |
The Lifetime ISA
For people aged 18 to 39. The government adds a 25% bonus, up to £1,000 a year, until you're 50. You can use it for a first home costing up to £450,000, or after age 60. Other withdrawals have a 25% charge, so you'd get back less than you paid in.
A worked example
With the calculator's default settings, a stocks and shares ISA with £5,000 to start and £300 a month, growing at 5% a year for 15 years, could be worth about £89,800, of which £59,000 is what you paid in.
Frequently asked questions
Cash or stocks and shares?
Cash is safer for short-term goals. Investments can grow more over five years or longer but can also fall.
Can I have more than one ISA?
Yes, you can pay into several types in the same tax year, as long as the total stays within £20,000.
For a pension, which gets tax relief on the way in, see our SIPP Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.