Savings Account Interest Calculator
Best rate: Trading 212
£19,412
after 3 years at 5.1% AER
Interest earned
+£2,212
Total deposited
£17,200
Balance Growth Comparison (Top 3)
- Trading 212
- Aldermore
- Chip
| Account | AER | Balance after 3yr | Interest | |
|---|---|---|---|---|
Trading 212 Cash ISA Cash ISA | 5.1% | £19,412 | +£2,212 | Open → |
Aldermore 1-Year Fix Fixed Rate | 5% | £19,365 | +£2,165 | Open → |
Chip Easy Access Top Rate | 4.84% | £19,292 | +£2,092 | Open → |
Plum Easy Access | 4.77% | £19,259 | +£2,059 | Open → |
Moneybox Easy Access ISA Available | 4.6% | £19,181 | +£1,981 | Open → |
Marcus by Goldman Sachs Easy Access | 4.3% | £19,045 | +£1,845 | Open → |
* Rates shown are indicative and subject to change. FSCS protection up to £85,000 per institution. Projections assume constant rate and monthly contributions.
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AER explained
AER (Annual Equivalent Rate) standardises how savings rates are quoted so you can compare accounts fairly, even if one pays interest monthly and another annually. It shows what the rate would be if interest were compounded once a year — always compare AER rather than a headline "gross rate," which can look higher but compound less frequently.
Getting the most from your savings
Check your Personal Savings Allowance
Basic-rate taxpayers can earn £1,000 in savings interest tax-free (£500 for higher-rate, £0 for additional-rate) — above this, interest is taxed as income, which is why ISAs matter more as rates rise.
Easy access vs fixed-rate trade-off
Fixed-rate bonds typically pay more but lock your money away — only use them for money you're confident you won't need before the term ends.
Spread large sums across institutions
FSCS protection covers £85,000 per person, per authorised institution — if you hold more than this in cash, split it across separate banking groups to stay fully covered.
Rates change — review annually
Introductory bonus rates on easy-access accounts often drop after 12 months. Set a reminder to review and switch if your rate falls behind the market.
Related tools
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Frequently Asked Questions
What is AER?
AER (Annual Equivalent Rate) shows the interest rate as if it were paid and compounded once a year, making it easy to compare savings accounts fairly.
What's the difference between easy access and fixed-rate?
Easy access accounts let you withdraw anytime but usually offer lower rates. Fixed-rate bonds lock your money away for a set period in exchange for a higher guaranteed rate.
Is my money protected?
Up to £85,000 per person per authorised institution is protected by the FSCS (Financial Services Compensation Scheme).
Should I use an ISA or a savings account?
ISA interest is tax-free. If you're a higher-rate taxpayer or have large savings, an ISA can save you money. Basic-rate taxpayers get a £1,000 Personal Savings Allowance anyway.
Key Terms Explained
Plain-English definitions of the financial terms used in this calculator.
- AER (Annual Equivalent Rate)
- The interest rate on savings accounts once compounding is included, showing what you would actually earn over a year. Use AER — not the headline gross rate — to compare savings accounts fairly.
- Compound Interest
- Interest earned on both your original money and on interest already added. Over long periods compounding accelerates growth dramatically — the earlier you start saving or investing, the more it works in your favour.
- Principal
- The original amount borrowed or invested, before any interest. On a repayment mortgage or loan, each monthly payment covers interest plus a slice of the principal until the balance reaches zero.
- ISA (Individual Savings Account)
- A UK account where interest, dividends and capital gains are completely tax-free. You can pay in up to £20,000 per tax year across Cash ISAs, Stocks & Shares ISAs and Lifetime ISAs.
Recommended Next Steps
Trusted partnersEarn up to 4.84% AER easy access. No lock-in, withdraw anytime.
Cash ISA at 5.10% AER — tax-free interest, instant access.
Easy access savings and Lifetime ISA with 25% government bonus.
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Not Financial Advice: This calculator is for informational and educational purposes only. Results are estimates and do not constitute financial advice, recommendations, or regulated advice. We are not authorised or regulated by the Financial Conduct Authority (FCA). Always consult a qualified financial adviser for personalised advice. Tax treatment depends on your individual circumstances and may change. Tax laws and rates may change. Past performance does not guarantee future results.
