Stocks and Shares ISA Calculator (UK)
Estimate how ISA investments could grow over time based on your contributions, an assumed return and your time horizon.
- Free
- No sign-up
- Uses the 2026-27 rules
Results are estimates only and not financial advice. Investments can go down as well as up.
Stocks & Shares ISA Calculator
Estimate value
Total deposited
Interest earned
The Advanced ISA Planner compares a cautious and a growth split of the same money over several tax years (one-off £14.99, no subscription).
Figures shown are rounded to the nearest pound. Unless you enter charges under More options, they are before fund and platform charges.
Advanced ISA Planner
Compare ISA scenarios side by side
£14.99 one-off, no subscription
Once you have an investment estimate, the Advanced ISA Planner can compare scenarios with different returns and mixes of ISA types side by side.
When a single calculator is not enough, the Advanced ISA Planner lets you set up longer-term scenarios, combine different ISA types, including cash ISAs, and model multiple tax years in one place.
- Combine Cash and Stocks & Shares ISAs
- Model multiple tax years and allowances
- Adjust returns, contributions, and time horizons
- Compare scenarios side by side
A paid tool: a one-off purchase of £14.99, with no subscription. The free calculators are separate from the planner. See the refund policy. Figures are illustrations, not forecasts.
What is a Stocks and Shares ISA?
A Stocks and Shares ISA is an Individual Savings Account for investments: you can hold funds, shares, bonds and other qualifying investments, and you pay no UK income tax or capital gains tax on the returns. You can pay in up to £20,000 each tax year across all your ISAs.
Use this Stocks and Shares ISA calculator to estimate how investments inside a UK ISA could grow tax-free over time. Unlike a Cash ISA, a Stocks and Shares ISA can rise and fall in value, but it may offer the potential for growth over the long term through funds, shares and diversified portfolios. You could get back less than you put in.
This tool estimates how monthly contributions, an initial lump sum and an assumed annual return could affect your final ISA value over a time horizon you choose. Investments can go down as well as up. Adjust the inputs to see estimated growth over your chosen time horizon.
If you’re comparing options, you may also want to use our Cash ISA Calculator for savings-style interest estimates. For deeper modelling, including risk profiles and side-by-side scenario comparisons, explore the Advanced ISA Planner.
How to use the Stocks and Shares ISA Calculator
Use this Stocks and Shares ISA calculator to estimate how regular contributions and lump-sum investments could grow over time, based on your chosen time horizon and assumed annual return.
- Add any initial investment and monthly contribution.
- Choose time horizon and estimated annual return.
- Review estimated outcomes.
How the Stocks and Shares ISA calculator works
The calculator adds your initial lump sum at the start and your monthly contribution at the end of each month. It divides the annual return you enter by 12 and compounds it monthly, so an entered 6% works out at about 6.17% over a full year. It shows the estimated value, the total you paid in and the growth. Used as a stocks and shares ISA returns calculator, the "estimated growth" tile is the return on what you paid in at the rate you chose.
Unless you open "More options: charges", the figures are before fund and platform charges; if you enter a percentage and/or a flat yearly charge, the calculator takes it off monthly and shows how much the charges you entered reduce the estimate. The calculator holds no charge data for any provider or fund, so you type in the figures from your own documents. The figures are before inflation, and they assume the same return every year. Real investment returns vary from year to year. The calculator does not check your contributions against the annual ISA allowance: use the ISA Allowance Checker for that.
Worked example
With the example inputs of a £1,000 initial investment, £300 a month, a 6% return and 10 years, the calculator estimates £50,983: £37,000 paid in and £13,983 of growth. This illustrates the maths; it is not a forecast.
Stocks and Shares ISA rules for 2026-27
- You can pay in up to £20,000 a tax year (6 April to 5 April) across all your ISAs, including any Cash ISA, Lifetime ISA or Innovative Finance ISA. Unused allowance does not carry over to the next tax year.
- You can split the allowance across more than one Stocks and Shares ISA in the same tax year, as long as the total stays within the limit (GOV.UK: how ISAs work).
- To move an existing ISA to another provider, ask the new provider for an ISA transfer rather than withdrawing the money yourself, or you may lose that part of your tax-free allowance (GOV.UK: transferring your ISA). See how to transfer an ISA.
- Under regulations made on 10 September 2026 (SI 2026/1018, read on legislation.gov.uk on 6 October 2026), from 6 April 2027, savers who are under 65 at the end of the tax year will be able to put no more than £12,000 a year of their allowance into cash ISAs. The overall limit stays at £20,000, so the rest can go into a Stocks and Shares ISA. The same regulations allow transfers from a stocks and shares or Innovative Finance ISA to a cash ISA if the ISA holder is 65 or over at the end of the tax year (GOV.UK).
ISA rules on this page are correct as of 26 September 2026. For every rule with its gov.uk source, see ISA rules at a glance.
Where to go next
Change the inputs
Change the monthly contribution, the time horizon or the assumed return and recalculate to see how each one changes the result.
Check ISA allowance usage
The ISA Allowance Checker shows how much of this tax year's allowance is left, from the amount already paid in.
Compare with a Cash ISA
The Cash ISA Calculator takes similar inputs. Investment values can go down as well as up, while cash ISA interest is set by the provider. Neither result is guaranteed.
Stocks and Shares ISA Calculator FAQs
This calculator estimates how a Stocks and Shares ISA could grow over time based on your contributions, time horizon and assumed rate of return.
No. Investments can rise and fall in value, and actual returns may be higher or lower than shown. This tool provides estimates only.
The rate entered is an assumption that depends on the ISA type being modelled. A lower rate gives a lower projected balance and a higher rate gives a higher one, and a higher rate can overstate potential growth. Actual returns are not guaranteed and can be lower.
No. ISAPlan gives you educational calculators and estimates only. You can use them to explore ISA ideas, but they do not replace advice from a regulated financial adviser.
Yes. Many users combine this with the ISA Allowance Checker or Contribution Split Planner to build a more complete ISA plan.