Savings Interest Calculator UK

AER stands for Annual Equivalent Rate. It shows the interest rate you would earn over a year if interest was compounded and paid once annually. AER makes it easy to compare savings accounts with different compounding frequencies (monthly, quarterly, etc.) because it standardises the rate to an annual figure. For example, an account with 4% AER will give you the same return over a year regardless of whether interest is compounded monthly or annually.

Compound interest is the concept of earning interest on your interest. When you save money, you earn interest on your initial deposit. When that interest is added to your balance, you then earn interest on both your original deposit AND the interest already earned. This creates a snowball effect where your savings grow faster over time. The more frequently interest is compounded (daily vs monthly vs annually), the more you earn, though the difference is usually small.

Monthly compounding means interest is calculated and added to your account balance 12 times per year, while annual compounding happens just once per year. With monthly compounding, each month's interest starts earning its own interest in subsequent months, resulting in slightly higher returns. For example, £10,000 at 5% AER for 5 years would grow to £12,833 with annual compounding versus £12,840 with monthly compounding - a small but real difference.

You may need to pay tax on savings interest depending on your income tax band and the amount of interest earned. Basic rate taxpayers have a Personal Savings Allowance of £1,000 per year (interest earned within this limit is tax-free). Higher rate taxpayers have a £500 allowance. Additional rate taxpayers have no allowance. Interest from ISAs (Individual Savings Accounts) is always tax-free regardless of your income. This calculator shows gross interest before any tax.

Savings interest rates vary with the Bank of England base rate and market conditions. As of 2024, competitive easy access savings accounts offer around 4-5% AER, while fixed-term accounts (where you lock your money away for 1-5 years) may offer slightly higher rates. Regular savings accounts sometimes offer the highest rates but with limits on how much you can deposit. Always compare AER when shopping around, and consider whether you need easy access to your money.

A common guideline is the 50/30/20 rule: 50% of income for needs, 30% for wants, and 20% for savings. Your first priority should be building an emergency fund of 3-6 months of essential expenses. Beyond that, your savings rate depends on your goals - retirement, house deposit, wedding, etc. Even small regular contributions add up significantly over time due to compound interest. This calculator can help you see how different monthly amounts affect your long-term savings.