ISA Calculator
Calculate your tax-free savings with Cash or Stocks & Shares ISAs
Last updated: August 2026 · 2026/27 allowances
ISA Type
Contributions
Annual: £2,400
Interest Rate
Typical: 3-5% (2026/27)
ISA Value After 10 Years
£38,075
100% tax-free
Tax-Free Growth
£9,075
Within Allowance
Annual contributions: £7,400 of £20,000 (2026/27)
ISA Allowance 2026/27
Remaining: £12,600
Tax Saved vs Taxable Account
Basic Rate (20%)
£1,815
Higher Rate (40%)
£3,630
Additional (45%)
£4,084
* Tax on interest if held outside ISA
Growth Over Time
Understanding ISAs
💷 Cash ISA
- • Savings account with tax-free interest
- • Capital guaranteed (FSCS protected)
- • Fixed or variable rates available
- • Easy access or notice accounts
- • Best for: Short-term goals, emergency funds
📈 Stocks & Shares ISA
- • Invest in stocks, bonds, funds
- • Tax-free dividends & capital gains
- • Higher potential returns (and risks)
- • Not capital guaranteed
- • Best for: Long-term growth (5+ years)
🏠 Other ISA Types
Annual Allowance 2026/27
£20,000
Total across all ISA types (except Junior ISAs)
⚠️ Coming April 2027
From 6 April 2027, the cash ISA limit will be cut to £12,000 for savers under 65 (Autumn Budget 2025). Your total £20,000 ISA allowance stays the same, only the cash portion is capped. Savers 65 and over keep the full £20,000 cash ISA limit.
✅ You Can
- • Split between Cash & S&S ISAs
- • Transfer old ISAs without losing tax-free status
- • Withdraw and re-deposit (flexible ISAs)
- • Have multiple ISAs (but only pay into one of each type per year)
❌ You Cannot
- • Exceed £20,000/year total
- • Open 2 Cash ISAs in same tax year
- • Transfer cash into previous years' ISAs
- • Use someone else's allowance
ISA allowance: £20,000 for 2026/27 tax year (6 April - 5 April)
Related calculators
Other free UK tools that follow on from this calculation.
Cash ISA vs Stocks & Shares ISA
Side-by-side projection of a Cash ISA vs Stocks & Shares ISA in real terms, with fees and the April 2027 cap.
Lifetime ISA Calculator
Project savings with the 25% government bonus for a first home or retirement.
Junior ISA Calculator
Project a child’s £9,000/year JISA pot at age 18, tax-free, Cash or S&S.
Future Value Calculator
Project how a lump sum or regular contributions grow over time with compound interest.
Reviewed by
Alexandre Bernier, LLM (UK), CFP®, CIM®, PFP®. Financial planner with 18 years in banking and wealth management, holding a UK master of laws and the Canadian CFP®, CIM® and PFP® designations. Writes and reviews every calculator and article on FinanceToolz.
Last updated: August 2026. How figures are sourced, reviewed and corrected is set out in our editorial policy. This is general information, not regulated financial advice.
Sources
Every rate and threshold used by this calculator is taken from the official pages below. If a figure here disagrees with one of these, the official page is right, please tell us.