Stocks & Shares ISA Calculator

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Use our stocks and shares ISA calculator to see how much tax free profits you can generate by investing instead of saving.

Selected Value: 5 %
Selected Value: 5 years
How much you have paid into your ISA.
How much profit your ISA has made over the years.

How To Use Our Stocks & Shares ISA Calculator

Here’s a step-by-step guide on how to use the Good Money Guide Stocks & Shares ISA Calculator and what to watch for. This calculator helps you see how much a Stocks & Shares ISA (for adults) might grow over time, based on how much you put in, how long you invest, and what rate of return you assume. It shows:

  • Final ISA Value:  your projected pot size
  • ISA Contributions: how much you’ve put in
  • ISA Returns: how much of that final value is growth (profit)

It’s useful for comparing different savings rates, time horizons, or return assumptions.

Field What it means Tips 
Initial ISA Contribution A one-off lump sum you invest right away If you’re starting from zero, use 0
Expected Annual Returns The rate you expect your investments to grow Default is 5 %. You could test lower (e.g. 3 %) or higher (e.g. 7 %)
Monthly ISA Contribution How much you’ll add every month This is in addition to the initial amount
Years Invested How many years you plan to leave the money invested E.g. if you plan to invest for 10 years, enter 10 Good Money Guide

Once you put in those inputs, the calculator gives you:

  • Final ISA Value
  • Total Contributions
  • ISA Returns (i.e. “growth above your contributions”)

How to calculate your Stocks & Shares ISA returns

  1. Go to the Stocks & Shares ISA Calculator page.
  2. Enter or adjust the Initial ISA Contribution.
  3. Set your Expected Annual Return (e.g. 5 %).
  4. Put in the Monthly ISA Contribution you plan to make.
  5. Enter Years Invested (how long you’ll leave the money invested).
  6. Click “Calculate” (or the equivalent).
  7. View the outputs: Final Value, Contributions, Returns.

Try changing the inputs (e.g. increasing monthly contribution, changing return assumption, lengthening years) to see how much difference those make.

Key Things to Remember & Caveats

  • The calculator does not include fees, platform costs, fund management fees, trading fees are not factored in.
  • The rate of return is an assumption, not a guarantee — market performance can be wildly different.
  • Contributions are limited by the annual ISA allowance (for stocks & shares ISAs).
  • Growth and withdrawals within an ISA are tax-free, which is a key advantage.
  • If you withdraw, you may lose the tax-efficient “wrapper” on that money (if the provider doesn’t allow replacing it).

How the Stocks & Shares Calculator Works

Let’s run a sample:

  • Initial ISA Contribution: £1,000
  • Monthly Contribution: £200
  • Expected Annual Return: 5 %
  • Years Invested: 15

You’d enter those into the calculator. It might output something like:

  • Total Contributions: £1,000 + (15 × 12 × £200) = £1,000 + £36,000 = £37,000
  • Final ISA Value: ~ £48,000–£55,000 (depending on compounding)
  • ISA Returns (Growth): ~ £11,000–£18,000

So your contributions of £37,000 over 15 years might grow to £50,000+ under that 5 % assumption — entirely tax-free inside the ISA.

Ready to start investing in a stocks and shares ISA?

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