Future Builder
Junior SIPP & Junior ISA Calculator
See how much your child's investments could grow to by age 18
Free UK calculator — including the 25% government tax relief on Junior SIPPs
Your child could have
£15,354
by age 18
Including £3,071 from government tax relief!
Your Contributions
£9,600
Over 8 years
Investment Growth
£3,354
From 6% annual return
Tax Relief Growth
£3,071
From £2,400 government bonus
Growth Projection
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Interested in Junior SIPPs? See the Lifetime Value!
This calculator shows what your child could have by age 18. But with a Junior SIPP, the government's 25% tax relief bonus keeps growing for 50+ more years until retirement. Our Tax Relief Calculator shows what that free money could become - often £100,000+!
Calculate Lifetime Tax Relief ValueHow the Calculator Works
Compound Growth
The calculator uses 6% annual growth (typical for diversified index funds) compounded monthly over time.
Tax Relief (SIPPs)
Junior SIPPs get 25% tax relief from the government (e.g., £2,880 contribution → £3,600 total).
Tax-Free Growth
Both Junior ISAs and SIPPs grow tax-free - no income tax or capital gains tax on investment returns.
Frequently Asked Questions
Is 6% a realistic growth rate?
Yes, 6% is a conservative estimate for a diversified global index fund over 10+ years. Historical returns for the FTSE Global All Cap Index average around 8-10% annually, but we use 6% to be conservative.
What's the difference between Junior ISA and Junior SIPP?
Junior ISAs are tax-free savings accounts accessible at age 18, with a £9,000/year limit. Junior SIPPs are children's pensions with 25% tax relief but accessible only at age 57+, with a £2,880/year contribution limit (£3,600 with tax relief). Read our full comparison.
How much can I pay into a Junior SIPP each year?
The annual Junior SIPP allowance is £2,880 of your own money per tax year. The government automatically adds 25% basic-rate tax relief on top, bringing the total invested to £3,600 a year.
Can I have both a Junior ISA and Junior SIPP?
Yes! Many parents use both - a Junior SIPP for long-term retirement savings (with tax relief) and a Junior ISA for shorter-term goals accessible at 18.
How is tax relief calculated for Junior SIPPs?
The government adds 25% (basic rate tax relief) to contributions. For example, if you contribute £240/month (£2,880/year), the government adds £720/year, making the total £3,600. This bonus also grows over time. Learn more about tax relief.
Learn More About Junior ISAs & SIPPs
What is a Junior ISA?
Complete guide to Junior ISAs - how they work, contribution limits, and who can open one.
Read more →What is a Junior SIPP?
Everything you need to know about Junior SIPPs including tax relief and contribution rules.
Read more →Junior SIPP Tax Relief
Understand how the 25% government bonus works and how much it could be worth over time.
Read more →