Savings Interest Calculator

Our savings interest calculator shows exactly how much interest you earn on any balance. AER (Annual Equivalent Rate) accounts for compounding and is the correct rate to compare across accounts.

How to Use the Savings Interest Calculator

Enter your savings balance and the annual interest rate (AER) from your account. AER — Annual Equivalent Rate — standardises rates across accounts with different compounding frequencies, making it the most reliable figure for comparison. All UK banks are required to quote AER, so always use this figure rather than the gross rate when comparing accounts.

The personal savings allowance (PSA) means basic-rate taxpayers can earn up to £1,000 in savings interest per year tax-free. Higher-rate taxpayers have a £500 PSA; additional-rate taxpayers have no allowance. Interest above the allowance is taxed at your marginal income tax rate. The calculator shows both gross interest and, where relevant, the after-tax figure based on your tax band selection.

For savings within an ISA, all interest is tax-free regardless of the amount or your tax band. If you regularly earn interest that would exceed your PSA, sheltering savings within a Cash ISA eliminates the tax liability permanently on those funds. The annual ISA allowance (£20,000 for 2026/27) resets each April — unused allowance cannot be carried forward, making each year’s allowance a use-it-or-lose-it opportunity.

Fixed-rate savings accounts and bonds offer higher rates than easy-access accounts in exchange for locking your money away for a set period. Use this calculator to compare the net return from a fixed-rate product at, say, 4.5% with an easy-access account at 3.8%, accounting for your PSA position. The difference in net return must be weighed against the loss of access to your money if circumstances change during the fixed term.