What is the Cash ISA vs Stocks & Shares ISA Calculator?
The Cash ISA vs Stocks & Shares ISA Calculator helps you compare the long-term growth potential of saving in a Cash ISA versus investing in a Stocks & Shares ISA. It models contributions, interest rates, investment growth and inflation to show how each option performs over time. It also includes the upcoming £12,000 Cash ISA cap from 2027–28 to give a realistic view of future ISA strategy.
How the Calculator Works?
You enter your ISA contributions, expected Cash ISA interest rate, investment growth assumptions and inflation rate. The calculator then runs both strategies side by side over your chosen time horizon. It applies the £12,000 Cash ISA limit where relevant and shows both nominal and inflation-adjusted balances. This allows you to see the potential long-term gap between cash savings (which may lose purchasing power) and market-based investing (which may grow faster but with volatility).
Step One: Enter Contribution and Growth Assumptions
Add your annual contributions, expected Cash ISA rate and investment growth rate. Set inflation if you want to view results in today’s money.
Step Two: Choose Your Time Horizon
Select how many years you want to model. Longer horizons highlight the compounding differences between cash and investing.
Step Three: Compare Long-Term Outcomes
Review projected balances with and without inflation. See how the proposed £12,000 Cash ISA cap affects overall savings and where Stocks & Shares ISAs may outperform over longer periods.
Disclaimer: This calculator provides illustrative projections only and is not financial advice. Investment returns can go up or down, and inflation can vary. Speak with a qualified financial adviser if you need personalised guidance.
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What is the Cash ISA vs Stocks & Shares ISA Calculator?
It is a UK-focused tool that compares long-term outcomes for Cash and Stocks & Shares ISAs, showing how interest, investment growth and inflation affect your savings over time.
What does this calculator compare?
It compares the long-term growth of saving in a Cash ISA versus investing in a Stocks & Shares ISA, with full flexibility to adjust contributions and growth assumptions.
How does the Cash ISA cap from 2027–28 work?
From April 2027, most savers can only place £12,000 per year into a Cash ISA. The overall ISA limit remains £20,000, so any additional savings must go into a Stocks & Shares ISA or another ISA type. The calculator applies this limit where applicable.
Why do Stocks & Shares ISAs often outperform Cash ISAs long term?
Cash ISAs offer stability but usually lose purchasing power over time due to inflation. Stocks & Shares ISAs carry investment risk but offer higher growth potential over periods longer than five years.
How does inflation affect Cash ISAs?
If inflation exceeds your Cash ISA interest rate, your real return becomes negative. Over long periods this can significantly erode purchasing power. The calculator can show inflation-adjusted results to illustrate this.
Are Stocks & Shares ISAs risky?
It depends on what you perceive as risky. You could argue that a cash ISA is riskier as the value of the money decreases with inflation. Stock Markets fluctuate, especially over the short term. However, over periods longer than five years, diversified investments have historically outperformed cash.
What information do I need?
You need expected contributions, Cash ISA rate, investment growth rate and an inflation figure if you want to view balances in today’s money.
Is this financial advice?
No. It is an illustrative planning tool.