Buy Now Pay Later Calculator

Work out exactly what you'll pay each period and in total on a Buy Now Pay Later plan.

Result

How it is calculated

The amount financed is F = price − down payment. The plan is treated as monthly payments with a monthly rate r = APR ÷ 100 ÷ 12, and the instalment is P = r × F ÷ (1 − (1 + r)^−n), where n is the number of instalments. With an APR of 0 the formula becomes P = F ÷ n. Total paid is P × n + down payment, and total interest is that total minus the price. Inputs that give no result: a price of zero or less, a down payment that is empty, negative or above the price, an instalment count that is not a whole number of at least 1, and an empty or negative APR. Fees, late charges and biweekly schedules are not modelled; amounts are in dollars.

Worked example

An item costs $1,200 and you pay $200 up front, financing the rest over 6 monthly instalments at 15% APR. Financed amount: 1,200 − 200 = 1,000. Monthly rate: 15 ÷ 100 ÷ 12 = 0.0125. Instalment: 0.0125 × 1,000 ÷ (1 − 1.0125^−6) = $174.03. Total paid: 174.03 × 6 + 200 = $1,244.20, so the interest is 1,244.20 − 1,200 = $44.20. The calculator shows an instalment of $174.03, with $1,000.00 financed. At 0% APR the same plan would be $166.67 a month.

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Common mistakes

  • Entering four biweekly payments as 4 instalments with a monthly APR. The tool assumes each instalment is one month apart, so the interest it shows will not match a biweekly schedule.
  • Entering the down payment as a percentage (such as 20). It is a money amount, and a value above the price gives no result.
  • Leaving the APR or down payment field empty for a 0% or no-deposit plan. Type 0; an empty field gives no result.
  • Typing a fractional instalment count such as 5.5. Only whole numbers work, so round to the real number of payments.
  • Comparing only the instalment and ignoring the total paid, or forgetting late fees and merchant surcharges, which are not in the figures shown.

Sources

About this calculator

Buy Now, Pay Later (BNPL) plans — offered by services like Klarna, Afterpay, Affirm, and PayPal Pay in 4 — let shoppers split a purchase into a series of installments, often four biweekly payments with 0% interest, or longer monthly plans that may charge interest depending on the provider and purchase amount. Retailers pay a merchant fee to offer BNPL at checkout because it tends to increase average order value and conversion rates, while consumers get short-term financing without a traditional credit card application.

Shoppers and personal-finance-conscious buyers use a BNPL calculator to see exactly what each installment will cost and what the total repayment adds up to before committing, since some plans charge interest or late fees that can make the effective cost higher than the sticker price — a distinction that matters because BNPL debt doesn't always appear on a traditional credit report the way a credit card balance does, making it easy to lose track of multiple concurrent plans.

This calculator takes your purchase price, any down payment, the number of monthly installments, and the annual interest rate (APR, use 0 for an interest-free plan), and returns the amount financed, your monthly payment amount, total cost, and total interest so you can compare a BNPL plan against paying in full or using a credit card. It assumes equal monthly payments and does not include late fees or other charges, so add those yourself if your plan has them. For a four-payment biweekly plan with 0% interest, enter 4 installments at 0% to see the amount of each payment.

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