Debt Calculator

How is the cost of a debt calculated?

This calculator works out how long it takes to clear a debt based on the balance, annual interest rate, and a fixed monthly payment. Each month, interest is charged on the remaining balance and the rest of your payment reduces what you owe.

The total repayable figure is the sum of every monthly payment until the balance reaches zero. The difference between that and the original debt amount is the total interest cost.

What does "interest as % of debt" mean?

This metric shows total interest as a percentage of the original balance. A higher percentage means a larger share of your payments goes towards interest rather than reducing the debt. It is a useful way to compare the true cost across different debts, rates, or payment amounts.

Key factors that affect cost

• Interest rate - higher rates mean more of each payment goes to interest, extending the payoff timeline.
• Monthly payment - larger payments reduce the balance faster, which means less interest accrues over time.
• Debt amount - a higher starting balance generates more interest in absolute terms, even at the same rate.

Things to keep in mind

• This calculator assumes a fixed interest rate and consistent monthly payments. Real-world debts may have variable rates or changing minimums.
• Some debts (such as credit cards) calculate interest daily rather than monthly, which can produce slightly different results.
• The results do not account for fees, penalties, or promotional rate periods.