ISA Calculator (2026-27): Tax-Free Savings Growth
See how your ISA could grow with regular monthly saving, the UK’s answer to a SIP. Includes the £20,000 allowance and the 25% Lifetime ISA bonus.
Updated for the 2026-27 tax year · Rates checked 14 October 2026
| Final value | £136,032 |
|---|---|
| In today’s money | £83,016 |
| Your deposits | £72,000 |
| Tax-free growth | £64,032 |
| Paid in during year one | £3,600 |
- Your ISA could be worth £136,032 after 20 years, with no tax on interest, dividends or gains.
Your result, explained
Saving regularly, your ISA could be worth £136,032: £72,000 from you and £64,032 of tax-free growth. In today’s money that’s about £83,016.
A monthly direct debit into an ISA works like a SIP: you buy more units when prices are low and fewer when high. For goals more than five years away a Stocks & Shares ISA has historically beaten cash, while a Cash ISA suits money you may need soon.
Growth by year
| Year | Deposits | Growth | Value |
|---|---|---|---|
| 1 | £3,600 | £98 | £3,698 |
| 2 | £3,600 | £320 | £7,618 |
| 3 | £3,600 | £555 | £11,773 |
| 4 | £3,600 | £804 | £16,177 |
| 5 | £3,600 | £1,069 | £20,846 |
| 6 | £3,600 | £1,349 | £25,794 |
| 7 | £3,600 | £1,646 | £31,040 |
| 8 | £3,600 | £1,960 | £36,600 |
| 9 | £3,600 | £2,294 | £42,494 |
| 10 | £3,600 | £2,648 | £48,742 |
| 11 | £3,600 | £3,022 | £55,365 |
| 12 | £3,600 | £3,420 | £62,384 |
| 13 | £3,600 | £3,841 | £69,825 |
| 14 | £3,600 | £4,287 | £77,713 |
| 15 | £3,600 | £4,761 | £86,074 |
| 16 | £3,600 | £5,262 | £94,936 |
| 17 | £3,600 | £5,794 | £104,330 |
| 18 | £3,600 | £6,358 | £114,288 |
| 19 | £3,600 | £6,955 | £124,843 |
| 20 | £3,600 | £7,589 | £136,032 |
Types of ISA
- Stocks & Shares ISA: invest in funds and shares. Best for goals five or more years away.
- Cash ISA: tax-free savings interest.
- Lifetime ISA: for ages 18–39 to open. Save up to £4,000 a year and the government adds 25%, for a first home or retirement from 60.
The 2026/27 allowance
You can put up to £20,000 into ISAs between 6 April 2026 and 5 April 2027, split however you like (a Lifetime ISA counts up to £4,000 of it). Unused allowance doesn’t roll over. From April 2027, under-65s will be able to put up to £12,000 of the £20,000 into cash ISAs.
Frequently asked questions
Is a Stocks & Shares ISA like a SIP?
Yes: a monthly direct debit into a Stocks & Shares ISA fund works like a SIP, with the added bonus that all growth and income are tax-free.
Do I pay tax when I withdraw from an ISA?
No. ISA withdrawals are tax-free (Lifetime ISA withdrawals for other purposes face a 25% charge).