Monthly Savings Interest Calculator UK 2026
Instantly calculate your monthly savings growth with compound interest. Estimate your final balance, interest earned, and tax implications for UK ISAs and standard accounts.
Savings Plan Details
Enter your savings details to estimate your final balance and interest earned
The starting amount in your savings account.
How much you plan to add every month.
The Annual Equivalent Rate (AER) offered by your bank.
How many years you plan to save for.
ISAs are tax-free. Standard accounts are subject to the Personal Savings Allowance.
Your Savings Projection
Estimated final balance, compound interest, and tax breakdown
Enter your savings details above and click Calculate Savings to reveal your projected balance and interest earned.
Monthly Savings Growth Scenarios 2026
Quickly reference how your monthly savings could grow over time with compound interest (assuming a 4.5% AER and Cash ISA tax-free status).
| Monthly Contribution | Interest Rate | Years | Total Contributions | Est. Interest Earned | Final Balance |
|---|---|---|---|---|---|
| £100 | 4.0% | 5 | £6,000 | £660 | £7,000 |
| £200 | 4.0% | 10 | £24,000 | £5,900 | £29,900 |
| £500 | 4.5% | 15 | £90,000 | £42,500 | £132,500 |
| £1,000 | 5.0% | 20 | £240,000 | £165,000 | £405,000 |
| £250 | 3.5% | 25 | £75,000 | £53,000 | £128,000 |
UK Savings Interest FAQ
Everything you need to know about compound interest, UK savings accounts, Cash ISAs, and the Personal Savings Allowance.
Monthly interest is calculated by dividing the Annual Equivalent Rate (AER) by 12. The interest is then applied to your balance each month. If you have compound interest, the next month’s interest is calculated on the new total, including previously added interest.
The Personal Savings Allowance (PSA) allows basic rate taxpayers to earn up to £1,000 in savings interest tax-free per year. Higher rate taxpayers can earn £500 tax-free, while additional rate taxpayers receive no allowance. Interest earned above these limits is subject to Income Tax.
No. Interest earned within a Cash ISA is completely tax-free. You do not need to declare it on your tax return, and it does not count towards your Personal Savings Allowance.
Compound interest means you earn interest on your initial deposit, on your monthly contributions, and on the interest that has already been added. By contributing monthly, you accelerate the compounding process, as each new contribution immediately starts earning interest for the remaining months.
Gross interest is the raw interest rate before tax. AER (Annual Equivalent Rate) shows what the interest rate would be if it was compounded and paid for a full year. AER allows you to easily compare different savings accounts, regardless of whether they pay interest monthly, annually, or at maturity.
No. Since April 2016, UK banks and building societies pay savings interest gross (without deducting tax). It is your responsibility to ensure you pay any tax due on interest that exceeds your Personal Savings Allowance, usually via Self Assessment or a change to your tax code.