ISA Calculator
Project the tax-free growth of your Stocks and Shares or Cash ISA.
Your result
Updates as you type. Based on 2025/26 UK figures where relevant.
How this is worked out
Each year's contribution is added at the start of the year and grows at your chosen rate. Growth inside an ISA is free of income tax and CGT. The annual allowance is £20,000.
Tips
- Pay off high-interest debt before saving beyond a basic emergency fund.
- Use your £20,000 ISA allowance each year where you can – it doesn't roll over.
- Check whether your savings rate beats inflation; if not, your money is losing value.
Guides for this calculator
More savings and loans calculators
Frequently asked questions
How does the iSA Calculator work?
Each year's contribution is added at the start of the year and grows at your chosen rate. Growth inside an ISA is free of income tax and CGT. The annual allowance is £20,000.
Are returns guaranteed?
No. Savings and investment projections are illustrations based on the rate you enter. Investments can go down as well as up.
What rate should I use for investments?
Many people test a cautious 4–5% and a more optimistic 6–7% to see a range of outcomes.
Is my savings interest taxed?
Basic-rate taxpayers have a £1,000 Personal Savings Allowance, higher-rate taxpayers £500. Interest inside an ISA is tax-free.
This calculator gives an estimate for general information. It isn't financial, tax, legal or medical advice. Check official figures on GOV.UK or NHS.uk, or speak to a qualified adviser.