ISA Calculator UK: How Much Could Your ISA Be Worth? (2026/27)
By Wealthvieu · Updated
See how your ISA contributions could grow over time with our ISA calculator. Compare different contribution amounts, time horizons, and growth rates to plan your tax-free savings strategy.
Table of Contents
ISA Allowance 2026/27
ISA Type
Annual Limit
Lifetime Limit
Cash ISA
Up to £20,000 (shared)
None
Stocks & Shares ISA
Up to £20,000 (shared)
None
Innovative Finance ISA
Up to £20,000 (shared)
None
Lifetime ISA
£4,000 (counts towards £20,000)
Until age 50
Total across all ISAs
£20,000
None
For full details on each ISA type, see our ISA guide.
ISA Growth Projections: Monthly Contributions
£200/month
Years
Cash ISA (3.5%)
S&S ISA (5%)
S&S ISA (7%)
S&S ISA (10%)
5
£13,070
£13,600
£14,260
£15,490
10
£28,380
£31,060
£34,600
£41,310
15
£46,310
£53,580
£63,360
£83,100
20
£67,310
£82,550
£104,190
£151,870
25
£91,890
£119,690
£162,120
£265,370
30
£120,660
£167,110
£244,090
£452,100
£500/month
Years
Cash ISA (3.5%)
S&S ISA (5%)
S&S ISA (7%)
S&S ISA (10%)
5
£32,680
£34,010
£35,650
£38,720
10
£70,950
£77,650
£86,500
£103,280
15
£115,780
£133,960
£158,410
£207,740
20
£168,270
£206,380
£260,470
£379,680
25
£229,730
£299,220
£405,290
£663,430
30
£301,660
£417,780
£610,230
£1,130,240
£1,000/month
Years
Cash ISA (3.5%)
S&S ISA (5%)
S&S ISA (7%)
S&S ISA (10%)
5
£65,350
£68,010
£71,290
£77,440
10
£141,910
£155,310
£173,000
£206,550
15
£231,550
£267,910
£316,810
£415,490
20
£336,540
£412,770
£520,930
£759,370
25
£459,460
£598,440
£810,580
£1,326,860
30
£603,310
£835,560
£1,220,460
£2,260,490
Max ISA: £1,666/month (£20,000/year)
Years
Cash ISA (3.5%)
S&S ISA (5%)
S&S ISA (7%)
S&S ISA (10%)
5
£108,870
£113,310
£118,770
£129,010
10
£236,430
£258,780
£288,200
£344,120
15
£385,790
£446,460
£527,830
£692,130
20
£560,770
£687,730
£867,790
£1,264,970
25
£765,620
£997,080
£1,350,560
£2,210,430
30
£1,005,150
£1,392,170
£2,033,240
£3,765,620
ISA vs Non-ISA: Tax Savings
Without an ISA, your investment gains are subject to tax:
Tax Type
ISA
Non-ISA (Basic Rate)
Non-ISA (Higher Rate)
Interest income
Tax-free
20% (above PSA)
40% (above PSA)
Dividend income
Tax-free
8.75% (above £1,000)
33.75% (above £1,000)
Capital gains
Tax-free
18% (above £3,000)
24% (above £3,000)
Tax Savings Example: £500/month for 20 Years (7% Return)
Component
ISA
Non-ISA (Higher Rate)
Total contributions
£120,000
£120,000
Growth (before tax)
£140,470
£140,470
Tax on gains
£0
~£33,000
Final value
£260,470
~£227,470
Tax savings
—
£33,000
Lifetime ISA (LISA) Calculator
The LISA adds a 25% government bonus on top of your contributions:
Monthly Contribution
Your Annual Total
Government Bonus
Total Annual
With Bonus After 10 Years (5%)
£100
£1,200
£300
£1,500
£19,430
£200
£2,400
£600
£3,000
£38,860
£333 (max)
£4,000
£1,000
£5,000
£64,770
LISA Eligibility:
Age 18-39 to open
Contribute until age 50
Use for first home (under £450,000) or retirement (after 60)
25% penalty on early withdrawal for other purposes
Allowance doesn’t carry over — contribute before 5 April
Start early
Even small contributions compound significantly over decades
Max your LISA first
25% bonus is guaranteed return (if eligible)
Choose global index funds
Low-cost diversification for S&S ISA
Don’t time the market
Regular investing smooths out volatility
Review fees
Platform + fund fees compound against you over time
Bottom Line
ISAs are one of the most powerful tax-free savings tools in the UK. Whether you use a Cash ISA for safety or a Stocks & Shares ISA for growth, the key is to start contributing regularly and take full advantage of your £20,000 annual allowance.
