CalculatorsSwitch calculator
How this works
Savings accounts don’t all quote rates the same way. Some show the AER, some a gross rate paid monthly, quarterly or yearly. The calculator turns each one into an AER, the rate you’d really earn over a year with interest added on interest, so you can compare like with like.
It then shows what each account would pay on your balance over a year and how far ahead the best one is. You can also convert a single rate between gross and AER.
What it assumes
- Your balance stays the same for a full year.
- Bonus rates that end within the year aren’t included.
- Tax on interest isn’t taken off.
Worked example
Two accounts on £10,000
- Account one pays 4.2% AER. Account two pays 4.15% gross, added monthly.
- Turned into an AER, account two pays 4.23%, so it’s actually the better deal, even though its headline rate looks lower.
- On £10,000 for a year, account one pays £420.00 and account two £422.99. The difference is £2.99.
- For context, Bank Rate was 3.75% in October 2026, and savings rates tend to move with it.
Worked out with the same maths as the calculator above.
What to do next
Common questions
What’s the difference between AER, gross and APR?
Gross is the yearly rate before compounding. AER is what you actually earn in a year once interest is added on interest, and is the figure to compare savings with. APR is for borrowing, not saving.
Is a small difference in rate worth switching for?
It depends on your balance. On £10,000, 0.1% is about £10 a year. Weigh that against any notice period, withdrawal limits or the hassle of moving, and check whether the rate includes a bonus that ends.
Is my money safe in a savings account?
UK banks and building societies are covered by the Financial Services Compensation Scheme. From 1 December 2025 it protects up to £120,000 per person, per banking licence.
Do I pay tax on the interest?
Only above your Personal Savings Allowance: £1,000 for basic-rate taxpayers and £500 for higher-rate. Cash ISA interest is always tax-free.