ISA Savings Calculator UK: How Much Can You Save in an ISA? (2026)
March 2026 · 8 min read
Quick Answer
The ISA allowance for 2026-27 is £20,000 per year. A Stocks and Shares ISA growing at 7% per year — maxing out £20,000 annually — would be worth approximately £566,000 after 15 years completely tax-free.
ISA Types Compared 2026
Choosing the right ISA depends on your goal, timeline and risk tolerance.
| ISA Type | Annual Limit | Returns | Best For |
|---|---|---|---|
| Cash ISA | £20,000 | 4-5% fixed | Short-term goals, safety |
| Stocks & Shares ISA | £20,000 | 6-9% long-term avg | Wealth building 5+ years |
| Lifetime ISA | £4,000 | 25% bonus + growth | First home or retirement |
| Junior ISA | £9,000 | Cash or stocks | Saving for children |
| Innovative Finance ISA | £20,000 | 5-10% (higher risk) | P2P lending exposure |
ISA Growth Projections (£20,000 Per Year)
How much your ISA could be worth at different growth rates assuming maximum annual contributions.
| Years | 4% (Cash ISA) | 7% (Stocks ISA) | 9% (Optimistic) |
|---|---|---|---|
| 5 years | £108,328 | £115,766 | £119,694 |
| 10 years | £240,122 | £275,905 | £304,425 |
| 15 years | £400,574 | £505,383 | £594,186 |
| 20 years | £595,962 | £819,910 | £1,027,455 |
| 30 years | £1,122,047 | £1,887,596 | £2,723,000 |
Calculate Your ISA Savings Growth
Use our free savings calculator — select £ British Pound to see your ISA projected value.
Calculate ISA Growth →Frequently Asked Questions
What is the ISA allowance for 2026-27?
The annual ISA allowance for 2026-27 is £20,000 per person. You can split this across different ISA types but the total cannot exceed £20,000. Unused allowance cannot be carried forward to the next tax year.
What is a Lifetime ISA and who should use it?
A Lifetime ISA (LISA) allows you to save up to £4,000 per year and receive a 25% government bonus (£1,000 maximum per year). It can be used to buy your first home (up to £450,000) or for retirement from age 60. Anyone aged 18-39 can open one.
Cash ISA vs Stocks and Shares ISA: which is better?
Cash ISAs offer safety and fixed returns of 4-5% in 2026. Stocks and Shares ISAs offer higher long-term growth potential of 6-9% per year but with market risk. For goals over 5 years Stocks and Shares ISAs historically outperform. For goals under 3 years Cash ISAs are safer.
Can I have multiple ISAs?
From April 2024 you can hold multiple ISAs of the same type simultaneously. You can contribute to a Cash ISA and a Stocks and Shares ISA in the same tax year as long as total contributions do not exceed £20,000.
What happens to my ISA if I move abroad?
You can keep your existing ISA if you move abroad but you cannot make new contributions while a non-UK resident. The ISA remains tax-free in the UK but your new country of residence may tax the income and gains.