Junior ISA Calculator
See how much your child’s Junior ISA could be worth by the time they turn 18, based on your current balance, monthly contributions, and expected growth rate.
Project Your Child’s JISA Growth
A Junior ISA lets you save or invest tax-free on behalf of a child, with the funds locked away until they turn 18. Use this calculator to see how regular contributions could add up over time.
How the Projection Works
Five steps from today’s balance to age 18
Enter the Current Balance
Start with whatever is already saved in the Junior ISA, or enter zero if the account is being opened for the first time.
Add a Monthly Contribution
Enter how much you expect to pay in each month, combining contributions from parents, grandparents, or anyone else paying in.
Set the Child’s Current Age
This determines how many years of contributions and growth remain until the account automatically becomes theirs at 18.
Choose an Expected Growth Rate
Cash JISAs typically assume a lower, steadier rate, while a Stocks and Shares JISA might assume a higher rate to reflect its investment risk and potential.
Review the Projected Value
See the estimated total at age 18, along with how much of that comes from contributions versus estimated growth.
Junior ISA Calculator
Enter your details for an instant projection
Monthly Contributions at a Glance
Illustrative projections starting from birth, assuming a 4% annual growth rate and no existing balance.
| Monthly Contribution | Total Paid In (18 yrs) | Estimated Growth | Estimated Value at 18 |
|---|---|---|---|
| £25 | £5,400 | £1,975 | £7,375 |
| £50 | £10,800 | £3,950 | £14,750 |
| £100 | £21,600 | £7,900 | £29,500 |
| £200 | £43,200 | £15,800 | £59,000 |
| £333 (near max) | £71,928 | £26,330 | £98,258 |
Junior ISA FAQ
Answers to the most frequently asked questions about Junior ISAs and how they grow.
The Junior ISA allowance is set each tax year and applies per child, combined across a Cash JISA and Stocks and Shares JISA if both are held. Check the current government guidance for the exact figure, as it can change annually.
Anyone can contribute to a child’s Junior ISA, including parents, grandparents, other family members, and friends, as long as total contributions across the tax year stay within the annual allowance.
No, in almost all cases funds in a Junior ISA are locked until the child turns 18. Early withdrawal is only permitted in exceptional circumstances, such as a terminal illness diagnosis.
At 18, a Junior ISA automatically converts into an adult ISA, and the funds become the child’s own to access and manage as they wish.