ISA Calculator
The ISA Calculator projects the tax-free growth of your Individual Savings Account. The annual ISA allowance is £20,000 in 2024-25. All interest, dividends, and capital gains within an ISA are completely free of UK tax.
Educational estimate. Calculator results are for planning and information only, not financial, tax, medical, legal, or engineering advice. Verify important decisions with official sources or a qualified professional.
ISA Calculator
Cash & Stocks and Shares ISA Growth
📐 Formula & Method
ISA Growth
All returns are tax-free inside an ISA. The calculator also shows the equivalent taxable account value for comparison.
LISA Bonus
LISA bonus only applies until age 50. Withdrawals for non-qualifying purposes incur a 25% penalty that recoups the bonus plus some of your own money.
📋 How to Use
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1
Enter your current ISA balance and planned annual contribution (max £20,000).
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2
Select ISA type and expected return rate.
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3
Set your tax rate to see the tax saving vs a taxable account.
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4
See projected ISA balance and tax saved over time.
ISAs — The UK's Most Powerful Tax-Free Wrapper
Every UK adult can save up to £20,000 per tax year in ISAs (2024-25). Interest from Cash ISAs, dividends from Stocks & Shares ISAs, and capital gains are all completely exempt from UK income tax and capital gains tax. Balances can be passed to a surviving spouse on death without losing ISA status.
The Lifetime ISA (LISA) is aimed at first-time buyers and retirement savers under 40. You can contribute up to £4,000 per year and receive a 25% government bonus (up to £1,000 per year). Funds can be used to buy your first home or accessed penalty-free from age 60.
🔬 Methodology & Accuracy
Formula: Uses the standard mathematical formula shown in the Formula & Method section above. All computations run client-side in your browser — no data is sent to our servers.
Data sources: Tax bands, contribution limits and regulatory rates are taken from official US (IRS, SSA) and UK (HMRC, gov.uk) publications for the current tax year, and updated when bands change.
Last reviewed: January 2025 · Accuracy: Results are precise to two decimal places using IEEE-754 double-precision arithmetic. Intended for educational and planning use only.
For informational purposes only. Results are estimates based on the inputs and formulas provided. For financial, tax, medical, or legal decisions, consult a qualified professional. Rates and regulations change — always verify current figures with official sources.