ISA Savings Calculator
Project the tax-free growth of a UK Stocks & Shares or Cash ISA with monthly contributions, capped at the £20,000 annual allowance.
For information and education only — not financial advice. Results are estimates based on the numbers you enter; check important decisions with a qualified professional.
How to use
- 1Enter your starting balance, monthly contribution and expected return.
- 2Choose the number of years; contributions above the annual allowance are capped.
How it's calculated
Balance grows monthly at return ÷ 12. Contributions are capped at the annual allowance (£20,000 since 2017/18). All growth and income inside an ISA is free of UK tax.
Frequently asked questions
What is the ISA allowance?
£20,000 per tax year (6 April to 5 April), split however you like across Cash, Stocks & Shares, Innovative Finance and Lifetime ISAs (LISA max £4,000).
Do I pay tax on ISA growth?
No — interest, dividends and capital gains inside an ISA are free of UK income tax and capital gains tax.
What return should I use?
Cash ISAs pay the quoted interest rate. For Stocks & Shares ISAs, 4–6% a year after fees is a common long-term assumption, with no guarantee.