Interest Calculator for United Kingdom
Calculate both Simple and Compound interest on your savings or loans.
Region: United Kingdom (GBP)
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Quick Tip
Enter the AER from the account you are considering; regular saver accounts often have a monthly deposit cap.
About This Tool
Why use Interest Calculator?
UK banks and building societies quote savings rates as AER (annual equivalent rate), which shows what you would earn over a year including compounding. That makes AER the figure to compare between easy-access accounts, fixed-rate bonds and regular savers.
Money in an ISA grows free of UK income tax and capital gains tax, within the annual ISA allowance. Outside an ISA, the Personal Savings Allowance lets many basic-rate and higher-rate taxpayers earn some interest tax-free. Eligible deposits at authorised UK banks and building societies are protected by the Financial Services Compensation Scheme (FSCS) up to its limit per person, per banking licence.
Key Benefits
AER-based growth
Model your balance using the same annual rate UK providers publish.
Regular saving
Add a monthly deposit to mirror standing orders into a regular saver or stocks and shares ISA.
Interest versus deposits
See how much of your future balance comes from interest and how much from your own contributions.
How to use Interest Calculator
- 1
Enter the AER from the account you are considering; regular saver accounts often have a monthly deposit cap.
- 2
Choose simple or compound interest.
- 3
Enter the principal amount.
- 4
Add the annual interest rate and the time period.
- 5
Compare the interest earned and the final amount.
Best use cases
Check the return on a fixed deposit or certificate of deposit before you lock money in.
See why compound interest overtakes simple interest on longer terms.
Verify the interest on a simple-interest personal or family loan.
Work through simple and compound interest homework with an instant check.
Interest Calculator FAQs
What is AER?
AER stands for annual equivalent rate. It shows the interest you would earn in a year if interest is compounded, so you can compare accounts that pay monthly and annually on equal terms.
Is my savings account protected in the UK?
Eligible deposits with UK-authorised banks and building societies are covered by the FSCS up to its compensation limit per person, per banking licence. Some brands share one licence, so check before spreading money across them.
Do I pay tax on savings interest?
Interest inside an ISA is tax-free. Outside an ISA, the Personal Savings Allowance covers some interest each year depending on your tax band; interest above it is taxed at your income tax rate.
Which currency does this interest calculator use?
Amounts are shown in British Pounds (GBP). The formulas are the same everywhere, so you can switch to another country version if you need a different currency.
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