Junior ISA Calculator (UK)

Estimate what regular saving into a Junior ISA could be worth when your child turns 18.

  • No sign up
  • UK focused
  • Results are estimates only

Not financial advice.

Correct as of . The ISA and tax rules on this page were last checked against gov.uk on this date. Figures are for the 2026/27 tax year unless a different year is stated. For every rule with its source, see ISA rules at a glance.

What is a Junior ISA?

A Junior ISA is a tax-free savings or investment account for a child. In the 2026/27 tax year, up to £9,000 can be paid in for each child, in total across their Junior ISAs. The money belongs to the child. They can take control of the account at 16, but cannot take money out until they turn 18.

Junior ISA Calculator

Estimated value at 18

Total paid in

Growth

Figures shown are rounded to the nearest pound. Illustrative only: not a forecast and not financial advice.

This assumes a steady return and regular payments. For a stocks and shares Junior ISA, the value can go down as well as up, and charges reduce returns. Results are not guaranteed.

Advanced ISA Planner

Compare ISA scenarios side by side

£14.99 one-off, no subscription

The Advanced ISA Planner is for adult Cash and Stocks and Shares ISA scenarios. It does not model a Junior ISA.

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
Explore the Advanced ISA Planner

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.

The planner's worked example with its default inputs: three result tiles for two scenarios and the difference between them, above a year-by-year chart of both scenarios with a shaded range
Worked example with the planner's default inputs. Illustrative scenarios, not a recommendation or a forecast.

How does the Junior ISA calculator work?

  1. Enter your child's age now. The calculator estimates growth to their 18th birthday, assuming they have just had a birthday.
  2. Add any lump sum and a regular monthly amount.
  3. Enter an assumed yearly return. For a stocks and shares Junior ISA it also shows a lower and a higher return, to give a range rather than one number.
  4. Each tax year's payments are checked against the Junior ISA limit for that year. Anything above the limit is left out, and the result tells you how much.

The result states which tax years' limits were applied. The limits come from our ISA rules table, which is checked against gov.uk.

Which Junior ISA rules does the calculator use?

  • Annual limit: £9,000 per child in 2026/27, across cash and stocks and shares Junior ISAs combined. The government has said it will stay at this level until April 2031.
  • Number of accounts: a child can have 1 cash Junior ISA and 1 stocks and shares Junior ISA.
  • Who can pay in: anyone can pay into a child's Junior ISA, within the limit. Parents or guardians with parental responsibility open and manage the account.
  • Access: the child can manage the account from 16 and withdraw from 18, when the Junior ISA becomes an adult ISA. gov.uk sets out exceptions if the child is terminally ill or dies.
  • A child cannot have a Junior ISA as well as a Child Trust Fund.

How does a cash Junior ISA differ from a stocks and shares one?

A cash Junior ISA pays interest, so the rate you enter is the interest rate. A stocks and shares Junior ISA is invested, so the value can rise or fall and the rate you enter is only an assumption. Which suits a child depends on the family's circumstances and how long the money is invested. This calculator does not recommend either. It shows the effect of the numbers you enter.

Frequently asked questions

What is a Junior ISA?

A Junior ISA is a tax-free savings or investment account for a child. It can be a cash Junior ISA or a stocks and shares Junior ISA. The money belongs to the child.

How much can be paid into a Junior ISA each year?

In the 2026/27 tax year, up to £9,000 can be paid in for each child, in total across their Junior ISAs. The government has said it will stay at this level until April 2031. The calculator checks each tax year's payments against the limit for that year and leaves out anything above it.

Who can pay into a Junior ISA?

Anyone can pay into a child's Junior ISA, within the limit. Parents or guardians with parental responsibility open and manage the account.

When can a child take the money out?

The child can take control of the account at 16, but cannot take money out until they turn 18, when the Junior ISA becomes an adult ISA. gov.uk sets out exceptions if the child is terminally ill or dies.

Can a child have a Junior ISA and a Child Trust Fund?

No. A child cannot have a Junior ISA as well as a Child Trust Fund.

Does the calculator say what a Junior ISA will be worth?

No. It gives an estimate from the figures you enter, up to age 18, when the Junior ISA becomes an adult ISA. The yearly return is an assumption, not a forecast. For a stocks and shares Junior ISA the value can go down as well as up, and charges reduce returns, so the result is not guaranteed. It is general information, not financial advice.

Does the calculator say whether cash or stocks and shares is better?

No. A cash Junior ISA pays interest, while a stocks and shares Junior ISA is invested, so its value can rise or fall. The two work differently, and the choice is a personal decision that depends on the family's circumstances and how long the money is invested. This calculator does not make it or recommend either: it shows the effect of the numbers you enter.

Sources

This calculator gives general information only. It is not financial advice or a recommendation to open or pay into any product.