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Stocks and shares ISA calculator

A stocks and shares ISA lets your investments grow without tax on the income or gains. Enter what you start with, what you add each month and the charges you pay. You will see a possible value after charges, the cost of those charges, and whether you stay within the £20,000 ISA allowance.

Checked 22 October 2026.

This calculator estimates growth for a stocks and shares ISA from a starting amount and monthly payments. It does not cover cash, Lifetime or Junior ISAs, tax on money held outside an ISA, or advice on what to invest in.
£

What you put in on day one.

£a month

What you add at the end of each month.

years

How long you leave the money in.

% a year

A guess, not a promise. Real returns go up and down.

% a year

Platform and fund charges added together.

% a year

Used to show the result in today's money.

Possible value after charges

£122,929.35

Your first-year payments of £8,600.00 are within the £20,000 ISA allowance for 2026 to 2027.

Total you pay in
£77,000.00
Growth after charges
£45,929.35
Value without charges
£135,007.83
Cost of charges
£12,078.48
Value in today's money
£82,727.93
First-year payments
£8,600.00
Show the working
  1. Net yearly rate = yearly growth minus yearly charges. Charges are taken off the growth rate.
  2. Monthly rate = (1 + net yearly rate) to the power of 1/12, minus 1.
  3. Possible value = starting amount × (1 + monthly rate) to the power of the months, plus each monthly payment × ((1 + monthly rate) to the power of the months − 1) ÷ monthly rate = £122,929.35.
  4. Each monthly payment is added at the end of the month. The starting amount is invested from the first month. If the monthly rate is effectively zero, the value is the starting amount plus the monthly payment × the months.
  5. Total you pay in = starting amount + monthly payment × months = £77,000.00.
  6. Growth after charges = possible value − total you pay in = £45,929.35.
  7. Value without charges uses the same formula with the yearly growth and no charges = £135,007.83.
  8. Cost of charges = value without charges − value after charges = £12,078.48.
  9. Value in today's money = value after charges ÷ (1 + yearly inflation) to the power of the years = £82,727.93.
  10. First-year payments = starting amount + 12 × monthly payment = £8,600.00.
  11. The allowance check adds your starting amount and 12 monthly payments and compares the total with £20,000. Payments that straddle 5 April are not split.
  12. Growth is smooth here, real markets are not.

What is a stocks and shares ISA?

A stocks and shares ISA is an account where you hold investments. GOV.UK says you do not pay tax on income or capital gains from investments in an ISA. The value can fall as well as rise, so you could get back less than you paid in.

How much can you pay into a stocks and shares ISA?

Each tax year, from 6 April to 5 April, you can save up to £20,000 across all your ISAs, split however you like. A Lifetime ISA takes up to £4,000 of that. From 6 April 2027 the cash ISA limit falls to £12,000 for under-65s, but the overall £20,000 stays.

ISA limits
LimitAmount
Overall ISA allowance, 2026 to 2027£20,000 a tax year, across all ISAs
Lifetime ISAUp to £4,000 a tax year, within the £20,000
Cash ISA from 6 April 2027£12,000 for under-65s, £20,000 for those aged 65 or over, within the £20,000

How does this calculator work out growth?

The calculator takes your yearly growth, subtracts your yearly charges, and turns the result into a monthly rate. Your starting amount grows from the first month and each monthly payment is added at the end of the month. Inflation is used only to show the result in today's money.

How much do charges cost over time?

Small charges add up over time. The table shows what £200 a month could grow to at 5% a year before charges. Higher charges take a bigger share of the growth, and the gap widens the longer you invest. MoneyHelper says charges can eat into the returns you receive.

What £200 a month could grow to at 5% a year before charges
Years0% charges0.5% charges1% charges1.5% charges
10£30,872.63£30,095.13£29,339.18£28,604.20
20£81,160.90£76,831.96£72,768.35£68,953.24
30£163,075.18£149,412.82£137,054.11£125,869.55

How long should you invest for?

MoneyHelper's beginner's guide to investing is aimed at savings goals more than five years away. There is no such thing as a no-risk investment, and if prices are lower than when you bought, you could lose money. This calculator uses a steady growth rate, but real markets do not move steadily.

Common questions

How much can I put in a stocks and shares ISA each year?

You can save up to £20,000 a tax year across all your ISAs, and you can split it between accounts. The tax year runs from 6 April to 5 April. A Lifetime ISA takes up to £4,000 of the £20,000. Use the ISA allowance calculator to check your own allowance.

Do I pay tax on a stocks and shares ISA?

GOV.UK says you do not pay tax on income or capital gains from investments in an ISA. Charges still apply, and the value can fall.

What growth rate should I use?

Nobody can know future returns. Try a cautious figure and a few others to see the range. The calculator's starting figure of 5% a year before charges is an example, not a forecast.

What charges should I include?

Add the yearly platform charge and the fund's ongoing charges figure (OCF). MoneyHelper says fund managers and other providers charge fees that can reduce your returns, and suggests checking the annual management charge and the OCF.

Will the April 2027 changes affect stocks and shares ISAs?

The overall £20,000 allowance stays. From 6 April 2027 the cash ISA limit falls to £12,000 for people under 65. GOV.UK also describes new rules on some transfers from stocks and shares ISAs into cash ISAs, so check its page before moving money.

What does today's money mean?

It reduces the future value by the inflation rate you enter, so you can see what it might buy at today's prices. Inflation changes, so treat the figure as an estimate.

Can I lose money in a stocks and shares ISA?

Yes. MoneyHelper says there is no such thing as a no-risk investment, and if prices are lower than when you bought, you could lose money. The calculator shows a smooth path, so it cannot show falls.

Sources

Checked 22 October 2026:

Nothing you enter leaves your device. General information, not financial or investment advice. ISA rules can change; check GOV.UK before paying in. The value of investments can fall as well as rise.