One Click Answers

OCAShopping

Share tool
FacebookPinterestEmail

Credit Card Purchase Interest Estimator

How much interest will this purchase cost on my card?

Enter a purchase, the card APR and your monthly payment to see the months and interest.

One Click Answers · Credit Card Purchase Interest Estimator
oneclickanswers.com/purchase-interest-estimator · Printed
About this tool & how to use it

What it does

Estimates the months and interest if you pay a credit card purchase off with a fixed monthly payment. An estimate, not advice.

How to use it

  1. Enter the purchase amount and the card APR.
  2. Enter what you would pay each month.
  3. Read the months to pay off, the interest and the total.

One click answer

Your answer will appear here.

Fill in the form and your answer will appear here.

Everything is calculated in your browser: the prices and numbers you enter are never sent anywhere or stored. We do not know any store's prices or tax rates, and these results are arithmetic, not advice to buy.

Assumptions

  • It assumes you add nothing else to the card and the rate does not change.
  • Paying the whole balance by the due date may avoid interest on some cards: check your card terms.
  • This is an estimate and does not encourage carrying debt.

Printed from oneclickanswers.com. Results are estimates based on what was entered; see the assumptions above.

How it works

Each month the interest is the balance times the APR / 12, added to the balance; then your payment is taken off. The last payment is smaller.

$1,200 at 24% APR with $100 a month takes 14 months and about $186 in interest.

If the payment is no more than the interest added each month, the balance would not go down, and the page says so.

Formulas and details
  • Interest for a month = balance x APR / 100 / 12. New balance = balance + interest - payment.
  • The simulation repeats until the balance reaches 0; the last payment is the remaining balance.

Assumptions

  • It assumes you add nothing else to the card and the rate does not change.
  • Paying the whole balance by the due date may avoid interest on some cards: check your card terms.
  • This is an estimate and does not encourage carrying debt.

Example

Input: The starting values already in the form

Result: If you pay $100.00 a month, this purchase would take about 14 months to pay off and cost about $185.98 in interest, $1,385.98 in all.

Questions

How much interest will a purchase cost on my card?

It depends on the APR and how much you pay each month. Enter yours to see.

What if my payment is too small?

If it does not cover the monthly interest, the balance would not shrink, and the page says so.

Last reviewed 2026-10-04.

Related tools

Try another answer