Stocks & Shares ISA Calculator
Estimate the future value of your investments inside a tax-free UK Stocks and Shares ISA. Account for platform fees, expected returns, and monthly contributions up to the £20,000 annual limit.
Last updated: May 2026
Max £1,666/mo (£20k/yr)
S&P 500 Historical Avg: ~10% (7% inflation-adjusted)
Total ISA Value
Total Contributions
£125,000
Tax-Free Growth
+£141,498
Compared to a standard General Investment Account (GIA), your ISA wrapper shields you from paying 20% tax on gains and dividends.
| Year | Contributed | ISA Balance | Tax-Free Growth |
|---|---|---|---|
| Year 1 | £11,000 | £11,555 | £555 |
| Year 5 | £35,000 | £42,507 | £7,507 |
| Year 10 | £65,000 | £94,502 | £29,502 |
| Year 15 | £95,000 | £166,579 | £71,579 |
| Year 20 | £125,000 | £266,498 | £141,498 |
Reviewed by Anjali Mehta
•Personal Finance AnalystA seasoned financial journalist and analyst. Anjali focuses on making complex financial data accessible and ensuring our tools provide practical, real-world value to users. All mathematical models and regulatory data points have been verified for the current 2026 fiscal period.
What is a Stocks & Shares ISA?
A Stocks and Shares ISA is a tax-efficient investment account available to UK residents. It allows you to invest up to £20,000 each tax year without paying any Capital Gains Tax (CGT) or Dividend Tax on your returns.
Unlike a Cash ISA which earns fixed interest, a Stocks & Shares ISA allows you to invest in funds, ETFs, bonds, and individual shares. While returns are not guaranteed and your capital is at risk, historical data shows that over the long term (10+ years), stock market investments typically outpace inflation and cash savings significantly.
How to use this calculator
- 1Set Initial Investment — Enter any lump sum you are starting with or transferring from a previous ISA.
- 2Plan Monthly Contributions — Input your regular monthly deposits. The tool caps this at £1,666/month to keep you within the £20k annual limit.
- 3Estimate Growth & Fees — Set a realistic annual return (e.g., 5-8%) and subtract your broker's platform & fund fees (usually 0.2% - 1%).
- 4See Tax Savings — Discover how much Capital Gains Tax you avoid over the years compared to a standard General Investment Account (GIA).
Formula & example
Final Value = P(1 + (r - f)/12)^(12t) + PMT * [((1 + (r - f)/12)^(12t) - 1) / ((r - f)/12)]
Example: £500/month for 20 years at 7% return with 0.5% platform fee.
- Total Contributed: £120,000
- Net Annual Return: 6.5%
- Final Tax-Free Value: ~£243,000
- Tax-Free Growth: ~£123,000
Benefits
Zero Capital Gains Tax
Keep 100% of your investment profits when you sell.
Zero Dividend Tax
Reinvest your dividends faster without losing a slice to HMRC.
Compound Interest Shield
As your portfolio grows, the tax shelter becomes exponentially more valuable.
Use cases
Long-Term Wealth Building
Regularly investing in global index funds to build a nest egg over 10-30 years.
FIRE Movement
Financial Independence, Retire Early followers use S&S ISAs to bridge the gap before accessing pensions.
Inflation Beating
Protecting purchasing power when cash savings rates fall below the rate of inflation.
Frequently asked questions
Can I have both a Cash ISA and a Stocks & Shares ISA?+
Yes, under new rules you can open and contribute to multiple ISAs of the same or different types in the same tax year, as long as your total contributions do not exceed £20,000.
What is a good return rate to estimate?+
Historically, global stock markets have returned around 7-10% annually before inflation. A conservative estimate for projections is usually between 5% and 7%.
Do platform fees matter?+
Yes, significantly. A 1% fee difference over 20 years can eat up tens of thousands of pounds of your final balance due to the loss of compound growth on those fees.