Junior ISA Calculator (2026/27)
See what a Junior ISA could be worth when your child turns 18: monthly saving, assumed growth and fees, within the £9,000 limit for 2026/27, plus the GOV.UK age rules. Results update instantly, with every step shown. No sign-up.
Growth is your assumption, not a forecast: stocks and shares can fall as well as rise. For a cash Junior ISA, use the interest rate and 0% fees. The projection assumes the £9,000 limit stays the same in future years.
- Total paid in£0
- Growth after fees£0
- Lost to fees by 18£0
- Paid in each year£0
- Allowance left this tax year£0
Quick answer
Saving £100 a month into a Junior ISA from age 0 could grow to about £32,806 by 18 at 5% a year after 0.5% fees, from £21,600 paid in. The 2026/27 limit is £9,000. Growth is an assumption, not a promise; investments can fall. Rules from GOV.UK, checked 18 October 2026; they can change.
Year by year to 18
Value at each birthday. Age 16, when your child can take control of the account, is highlighted.
| Age | Paid in | Value after fees | Value with no fees |
|---|
Junior ISA rules 2026/27
| Rule | GOV.UK |
|---|---|
| Annual limit | £9,000 in the 2026 to 2027 tax year, across all the child's Junior ISAs |
| Who can have one | Under 18 and living in the UK (Crown servant exception) |
| Accounts | Up to 1 cash and 1 stocks and shares Junior ISA |
| Who opens it | A parent or guardian with parental responsibility for under-16s; 16 and 17 year olds can open their own |
| Control | The child can take control at 16 |
| Withdrawals | Not until 18 (exceptions for terminal illness or death); then it becomes an adult ISA |
| Tax | No tax on interest, capital growth or dividends |
Anyone can pay into a Junior ISA, but the money belongs to the child. You cannot transfer money between a Junior ISA and an adult ISA, and a child cannot have a Junior ISA as well as a Child Trust Fund.
The GOV.UK example, reproduced
“If your child has £2,000 paid into their cash Junior ISA from 6 April 2026 to 5 April 2027, only £7,000 could be paid into their stocks and shares Junior ISA in the same tax year.” The “allowance left this tax year” line does the same sum, and an automated test checks it.
About the projection
- Contributions are paid at the end of each month and capped at £750 a month (£9,000 a year).
- Growth and fees are applied monthly: (1 + growth)1/12 × (1 − fee)1/12. Results are in today's pounds only if you enter growth after inflation.
- GOV.UK only publishes the limit for the current tax year; future limits may change.
The formula
- g — assumed yearly growth before fees
- f — yearly fees as a percentage of the pot
- months — (18 − age now) × 12
See the formula with your own numbers
These update live from the calculator inputs above.
Frequently asked questions
What is the Junior ISA limit for 2026/27?
GOV.UK: in the 2026 to 2027 tax year, the savings limit for Junior ISAs is £9,000. Anyone can pay in, but the total paid into a child's Junior ISAs cannot go over £9,000 in the tax year.
Who can have a Junior ISA?
A child must be under 18 and living in the UK (children living abroad qualify only if a parent is a Crown servant and they depend on that parent for care). A child cannot have a Junior ISA as well as a Child Trust Fund; the fund can be transferred into a Junior ISA.
When can my child take the money out?
The child can take control of the account at 16 but cannot withdraw the money until they turn 18. At 18 the Junior ISA automatically turns into an adult ISA.
Can a child have a cash and a stocks and shares Junior ISA?
Yes, one of each. The £9,000 limit is shared: GOV.UK's example says if £2,000 is paid into the cash Junior ISA, only £7,000 could go into the stocks and shares Junior ISA in the same tax year.
Is a Junior ISA tax-free?
Yes. GOV.UK says you will not pay tax on interest in a cash Junior ISA, or on capital growth or dividends in a stocks and shares Junior ISA.
Method & sources
- Calculation: month-by-month growth at your assumed rate, less your fee, plus monthly contributions capped at the £9,000 yearly limit, until the child turns 18.
- Limit £9,000 for 2026 to 2027, eligibility, accounts, age 16 and 18 rules and the £2,000 / £7,000 example: GOV.UK — gov.uk/junior-individual-savings-accounts (add money, manage an account).
- All sources checked 18 October 2026. Verification: automated tests, run before every update, including the GOV.UK example and a closed-form check of the projection.
- Reviewed: .
Educational estimate only, not personal financial advice. Investment growth is not guaranteed and the value can fall. Rules can change and depend on your circumstances; confirm with GOV.UK or your provider.
Run your own numbers
Enter your child's age and monthly saving to see the projected pot at 18.
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