What is an Installment Plan (BNPL) Calculator?
Buy Now, Pay Later (BNPL) and installment plans let you split a purchase into several equal payments over time. This calculator shows exactly how much each payment will be, how much you pay in interest or service fees, and the total amount you will repay. It works for any currency — just enter your numbers.
How to use it
Enter the purchase price, the total interest or fee rate applied to the plan (as a percentage — use 0 if the plan is fee-free), and the number of installments. The calculator instantly returns the payment due each period plus a breakdown of total interest and total payable.
The formula explained
The total amount payable is the price plus a flat fee: \(\text{total} = \text{price} + \text{price} \times \text{rate}\). That total is then split evenly across the installments: \(\text{perInstallment} = \text{total} \div \text{installments}\). This models the common BNPL structure where a single flat fee (not compounding monthly interest) is added to the purchase and divided into equal chunks.
$$\text{Per Installment} = \frac{\text{Price} \times \left(1 + \frac{\text{Rate (\%)}}{100}\right)}{\text{Installments}}$$
Worked example
Suppose you buy a $1,200 laptop on a plan with a 10% fee paid over 4 installments. The total payable is $$1{,}200 + 1{,}200 \times 0.10 = \$1{,}320.$$ Divided by 4 installments, each payment is $330. You pay $120 in fees overall.
FAQ
Is this monthly interest (APR)? No — this calculator treats the rate as a single flat fee on the purchase, which matches most short-term BNPL plans. For amortizing loans with compounding interest, use a loan calculator instead.
What if my plan has no fees? Enter 0 for the interest/fee rate. The price will simply be split evenly across your chosen number of installments.
Does the number of installments change the total cost? Not in this flat-fee model — the total payable stays the same; more installments just mean smaller individual payments.
