Estimate future ISA growth and check your remaining 2026/27 ISA subscription allowance.
This is a planning estimate. Returns, rates, charges and tax rules can change. Stocks and shares can fall as well as rise, and the result is not guaranteed.
How to use the ISA Calculator UK
Enter the current ISA balance, the amount subscribed during the 2026/27 tax year, your planned monthly contribution, estimated annual return and investment period. The calculator estimates future value, total contributions, growth and remaining current-year allowance.
How the ISA growth estimate is calculated
| Result | Method |
|---|---|
| Existing balance growth | Current balance compounded monthly |
| Contribution growth | Future value of end-of-month contributions |
| Total contributions | Current balance + monthly contributions |
| Estimated growth | Future value − total contributions |
| Remaining 2026/27 allowance | £20,000 − current-year subscriptions |
ISA allowance for the 2026/27 tax year
GOV.UK states that the maximum amount an adult can subscribe to ISAs in the 2026/27 tax year is £20,000. The allowance is shared across eligible adult ISA types. Check the official Individual Savings Accounts overview before making contributions.
Cash ISA and stocks and shares ISA estimates
The same growth formula can illustrate a fixed assumed rate, but risk differs. Cash returns may change when rates are variable. Stocks and shares returns are uncertain and can be negative. Product charges are not included, so subtract expected fees or use a net return assumption.
Related calculators
Plan a general savings goal with the Savings Calculator UK. Compare simple and compound growth using the Interest Calculator. Review retirement options with the Pension Transfer Value Calculator and Pension Pot Calculator UK. Browse more tools on the United Kingdom Calculator homepage.
Frequently asked questions
What is the adult ISA allowance for 2026/27?
The overall adult ISA subscription limit is £20,000 for the 2026/27 tax year.
Does an ISA transfer use the annual allowance?
A properly completed ISA transfer normally does not count as a new subscription. Follow the provider’s transfer process rather than withdrawing and redepositing the money.
Are ISA returns guaranteed?
No. Cash rates can change, and investment values can fall. The calculator uses a constant assumed return only for illustration.
Does this calculator include provider charges?
No. Enter an estimated annual return after charges if you want fees reflected in the projection.
When does the ISA allowance reset?
The ISA subscription allowance applies by UK tax year, which runs from 6 April to 5 April.