Total Interest Calculator UK
This total interest calculator is built for people managing more than one account at once. Instead of looking at a single savings balance in isolation, you can enter multiple savings accounts, investment pots and debt balances to see your combined interest position.
It is useful for comparing how your money is working across cash savings, ISAs, general investment accounts, mortgages, loans or credit card balances. You can also set monthly contributions or overpayments and choose an optional maximum balance cap for contributions plus a separate interest-bearing balance cap where interest should only apply up to a certain balance.
What this tool can show you
- Total estimated interest earned per day, month and year at current balances
- Total estimated interest paid on debt accounts
- Net interest position across all accounts
- Projected balances for each account over your chosen timeframe
- A balance chart and a monthly interest chart
- Year-by-year summaries and account-level breakdowns
How to use the calculator
Add each account you want to track, choose whether it is an asset or debt, enter the current balance, annual interest or return rate, and any monthly contribution or overpayment. If an account should stop accepting new money once it reaches a certain size, set a balance cap. If interest should only be paid up to a certain balance, set the interest-bearing balance cap as well. Then choose how many years you want to project forward.