ISA Growth Calculator
Our ISA calculator projects tax-free ISA growth. You can save up to £20,000/year in 2026/27.
ISA Types
- Cash ISA: tax-free interest
- Stocks and Shares ISA: tax-free investing
- Lifetime ISA: £4,000/yr + 25% government bonus
ISA Growth Calculator
Project how much your ISA could grow over time — all interest and returns are tax-free.
Enter your annual ISA contribution and the expected annual return. The ISA allowance for 2026/27 is £20,000. All growth inside an ISA is tax-free indefinitely — you never pay income tax on interest or capital gains tax on investment growth, regardless of how large the pot becomes. For a Cash ISA, use the current AER; for a Stocks and Shares ISA, a planning assumption of 5-7% per annum is commonly used, though actual returns are not guaranteed. The calculator shows the projected balance year by year. Note that unused ISA allowance cannot be carried forward to future tax years — each year’s £20,000 is use-it-or-lose-it. Also note that contributing to a Lifetime ISA counts toward the overall £20,000 limit.