Our savings calculator estimates how much your money will grow over time, based on your starting balance, monthly contributions, and interest rate. Here’s exactly what’s happening under the hood — and how to get the most accurate results.
The formula: compound interest
The calculator uses compound interest, which means you earn interest on your interest — not just on your original deposit. This is why starting early makes such a dramatic difference to your final balance.
What each field means
Starting balance: How much you have saved right now. Enter 0 if you’re starting from scratch.
Monthly contribution: How much you plan to add each month. Even £50 makes a meaningful difference over time.
Interest rate (AER): Use the AER (Annual Equivalent Rate) shown by your savings provider. This is the standardised rate that accounts for compounding, making it easy to compare accounts fairly.
Time period: How long you want to save for — months or years.
What the results show
Final balance: The total amount in your account at the end of the period — your original savings plus all contributions plus all interest earned.
Total contributions: The sum of your starting balance plus all the monthly payments you’ve made.
Total interest earned: The difference between your final balance and total contributions — this is the money the account generated for you.
Important caveats
Rates are variable. Easy access savings rates can change at any time. The calculator shows what you’d earn if the rate stayed constant — in reality it may go up or down.
Tax is not included. Most UK savers don’t pay tax on savings interest due to the Personal Savings Allowance (£1,000 for basic rate taxpayers). But if your interest income exceeds this, your actual take-home will be slightly less than shown.