Junior ISA Calculator
Calculate how much a Junior ISA will be worth when your child turns 18. Tax-free growth with £9,000/year limit.
Last updated: April 2026 · Source: GOV.UK
Max £9,000/year
Value at Age 18
£29,324.28
16 years of deposits remaining
Total Deposited
£19,200.00
Tax-Free Growth
£10,124.28
Annual Deposit
£1,200.00
Junior ISA: tax-free savings for under 18s. £9,000/year limit. Child gains access at 18. Available as Cash or Stocks & Shares JISA. Cannot be withdrawn before 18 (except terminal illness).
Disclaimer
This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.
How It Works
Junior ISAs have an annual contribution limit of £9,000 per child per tax year, available from birth until age 18. Any UK resident child under 18 who does not have a Child Trust Fund can have a JISA. Parents, grandparents, and anyone else can contribute, but the total from all sources cannot exceed £9,000. The child takes ownership at 18 and can withdraw or continue holding the ISA as an adult ISA.
The compound growth calculation is particularly powerful for JISAs because of the long time horizon (up to 18 years). At 6% annual growth, £9,000 contributed every year for 18 years grows to approximately £311,000 — of which £149,000 is pure investment growth. Even modest contributions of £100/month over 18 years at 6% growth produce approximately £38,700, nearly double the £21,600 contributed.
Cash JISAs offer guaranteed returns at a fixed or variable interest rate, suitable for shorter time horizons. Stocks and Shares JISAs invest in funds or shares and are generally recommended for JISAs because the 18-year time horizon smooths out short-term volatility. The calculator shows both scenarios side by side, illustrating how even modest differences in average return (e.g., 4% cash vs 6% equities) compound to substantial differences over 18 years.
Junior ISA: £250/month from birth to age 18
- Monthly contribution: £250 (£3,000/year, within £9,000 limit)
- Total contributed over 18 years: £3,000 x 18 = £54,000
- At 6% annual growth (Stocks & Shares JISA): approximately £103,400 at age 18
- Investment growth: £103,400 - £54,000 = £49,400 tax-free gains
- At 3% growth (Cash JISA): approximately £70,100 — £33,300 less than the equities scenario
Source: GOV.UK
Frequently Asked Questions
- What does the Junior ISA Calculator do?
- Calculate how much a Junior ISA will be worth when your child turns 18. Tax-free growth with £9,000/year limit. All calculations are performed in your browser using official UK rates and thresholds.
- Is this calculator suitable for financial decisions?
- This calculator provides estimates for guidance only. Investment returns are not guaranteed and your capital is at risk. Consider seeking independent financial advice before making investment decisions.
- Are ISA contributions tax-free?
- Yes. The annual ISA allowance for 2025/26 is £20,000. Any interest, dividends or capital gains within an ISA are completely tax-free.