What this estimate includes
This calculator is designed for a quick planning comparison, with every important assumption visible. It includes:
- Current balance, APR, and monthly payment
- A steady extra amount applied monthly
- Estimated time and interest under both scenarios
How the calculation works
Monthly interest ≈ remaining balance × (APR ÷ 12); payment reduces interest first, then principal.
Results update as you type. Rounding happens for display; calculations use the full values entered. A real statement, pay stub, contract, or account agreement may use different timing and rules.
A worked example
On a $12,000 balance at 18.9%, increasing a $350 payment by $100 can remove many months and thousands in interest from the estimate.
Important limitations
This is an educational estimate, not financial, tax, legal, or employment advice. It cannot account for every local rule, fee, benefit, deduction, compounding convention, or personal circumstance. Use it to understand direction and scale, then verify an important decision with the relevant employer, lender, account provider, or qualified professional.
Frequently asked questions
Should I pay extra before saving?
A small emergency buffer can help prevent new debt when an unexpected bill appears. The right balance depends on stability and risk.
Will my lender apply the extra to principal?
Check the lender’s instructions. Some loans may advance the due date or allocate payments differently unless you specify principal.
Reviewed August 17, 2026. We review formulas and explanations for clarity. If you spot a problem, please tell us.