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Cash ISA Calculator (UK)

Estimate how regular savings could grow in a Cash ISA, using a fixed interest rate.

No sign up. UK focused. Results are estimates only.

Not financial advice

Cash ISA Calculator - Estimate Tax-Free Savings Growth

Use this Cash ISA calculator to estimate how your savings could grow tax-free over time at a fixed or assumed interest rate. A Cash ISA allows UK savers to earn interest without paying income tax on returns, up to the £20,000 annual ISA allowance.

This tool is ideal for those prioritising capital stability and predictable returns. Adjust your starting balance, monthly contributions and interest rate to see how your ISA value may grow over your chosen time horizon.

If you are comparing savings against investment-based ISAs, explore our Stocks and Shares ISA Calculator for growth projections with market exposure. For scenario modelling across different ISA types and contribution strategies, use the Advanced ISA Planner.

New to ISAs? Visit our ISA Guides to understand how the allowance works and how Cash ISAs compare to other options.

Cash ISA Calculator

Initial lump sum (£)

Monthly contributions (£)

Time horizon (years)

Expected annual return (%)

Estimated Cash ISA value after X years

£-

Estimate value

£-

Total deposited

£-

Interest earned

Figures shown are rounded to the nearest pound

This assumes a constant interest rate and regular deposits. Rates can change and returns are not guaranteed.

Advanced planning

Advanced ISA Planner

For those who want a deeper view, the Advanced ISA Planner helps you explore longer-term scenarios, combine different ISA types, including cash ISAs, and model multiple tax years in one place.

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It's designed for users who want more flexibility and insight than a basic calculator can provide.

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  • Combine Cash and Stocks & Shares ISAs

  • Model multiple tax years and allowances

  • Adjust returns, contributions, and time horizons

  • Compare scenarios side by side

Free calculators remain avaliable. No subscription required to get started.

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How to use the Cash ISA Calculator​

Use this Cash ISA calculator to estimate how your savings could grow over time. Enter an initial deposit, monthly contributions and an assumed interest rate to see projected balances. Results are estimates only and based on UK Cash ISA rules.

  1. Add an initial amount and monthly contribution.​

  2. Choose an interest rate.

  3. See projected savings.​

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What people often do next

Review & refine

Try a different interest rate or time horizon to see how sensitive the outcome is.

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Learn more about how cash ISAs work, including rates and access rules.

Check allowance usage

See how much ISA allowance you still have available this tax year.

Compare cash vs investing

Some users compare Cash ISA returns with investment-based ISAs to understand the potential trade-off between certainty and growth over time.

Cash ISA Calculator FAQ's

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