How this calculator works
Interest is added monthly before payment. The last payment is reduced to the remaining amount due. A payment that only covers interest or less cannot reduce principal and is rejected. The estimate assumes no new spending, fees or rate changes and stops at 100 years.
The formula
Monthly interest = balance × annual rate / 1200
Payment made = smaller of regular payment and balance plus interest
New balance = balance + interest − payment made.A quick example
A 1,000 debt at 0% with a 300 monthly payment takes 4 payments. The first three are 300 and the last is 100; total paid is 1,000.
How to use this calculator
- Enter current debt and the annual nominal interest rate.
- Enter the amount you can pay each month.
- Calculate payoff time and interest, or increase the payment if principal cannot decrease.
A few common questions
Why is my payment too low?
It does not exceed the first month’s interest, so the balance will not decrease.
Is the final payment a full payment?
No. The calculation pays only the remaining balance plus that month’s interest.
Does this handle a credit card minimum payment?
It models a fixed amount, not a changing minimum-payment rule or additional card spending.