BNPL vs Credit Card Cost Calculator
Compare Buy Now, Pay Later vs credit card cost over the same months
How to use this BNPL vs credit card cost calculator
This BNPL vs credit card cost calculator shows which option actually costs you less over the same number of months. Instead of guessing from “0% interest” headlines or headline APRs, you see the total dollars paid in each scenario and the difference between them.
1. Start with the purchase and how long you’ll take to pay
In the first step, enter the purchase amount and how many months you expect to take to pay it off. The tool uses that same payoff period for both options:
- BNPL installments spread evenly across those months.
- Credit card payments sized to fully pay the balance in that time.
This keeps the comparison fair: you’re matching “pay it off in X months” either way.
2. Set the BNPL cost as a simple percentage
Many buy now, pay later plans advertise 0% interest, but can still charge late fees, payment change fees, or other charges if you miss terms. To keep inputs simple, the calculator uses one field: BNPL total cost (% of purchase).
Leave this at 0% to model a perfect on-time pay-in-four style plan with no fees. If you want to allow for a couple of late fees or other charges, add a few percent (for example 3–10%) as a rough “all-in” cost.
3. Plug in your real credit card APR
In the credit card box, enter the APR on the card you’d use. Statements usually list this in the rate table as “purchase APR.” The calculator converts APR into a monthly rate and solves for the fixed monthly payment that would pay off the purchase in the months you entered, then calculates total interest paid over that period.
4. Read the side-by-side breakdown
After you hit Calculate, the summary highlights:
- Total paid with BNPL and BNPL fees in dollars.
- Total paid on the card and credit card interest in dollars.
- Which option is cheaper and by how much in USD.
- Approximate simple annual cost of the BNPL plan vs the card APR.
The headline line calls out the cheaper choice over your chosen timeframe (for example: “BNPL cheaper by $48 over 6 months” or “Credit card cheaper by $26 over 3 months”).
5. Use the copy button for quick what-ifs
The Copy summary button creates a clean text breakdown you can paste into notes, budgeting sheets, or a shared doc when you’re comparing multiple offers. Try different:
- payoff periods (3 vs 6 vs 12 months),
- BNPL % costs to reflect risk of fees, and
- credit card APRs (promo vs regular rates).
This tool won’t tell you what to do, but it makes the trade-offs visible so you can choose with clearer numbers instead of marketing language.
How the BNPL vs credit card math works
Under the hood, this calculator treats BNPL as a flat percentage cost on the purchase, and the credit card as a standard amortizing balance paid off in equal monthly payments.
Let:
- P = purchase amount in USD,
- n = number of months to pay it off,
- b = BNPL cost percent as a decimal (for example 0.08 for 8%),
- A = annual credit card APR as a decimal (for example 0.2499 for 24.99%).
For BNPL, the calculator assumes one blended cost on the purchase:
BNPL fees = P × b
BNPL total paid = P + (P × b)
It then spreads that total evenly over n months:
BNPL monthly payment = BNPL total paid ÷ n
To give a rough sense of how “expensive” the BNPL plan is, the tool also computes a simple annualized cost by dividing b by the fraction of a year you’re borrowing for. This isn’t a formal APR, but it’s a useful ballpark comparison against the card’s APR.
For the credit card, the calculator converts APR into a monthly rate:
r = A ÷ 12
If r > 0, it solves for the fixed monthly payment M needed to pay the balance in exactly n months using the standard loan formula:
M = P × r ÷ (1 − (1 + r)−n)
Total paid and interest are then:
Card total paid = M × n
Card interest cost = Card total paid − P
When r = 0 (0% APR), the math simplifies: monthly payment is just P ÷ n and interest cost is $0. The calculator finally compares total BNPL cost vs card cost and reports which is lower along with the dollar difference so you can see the impact in plain language.
References and further reading
- CFPB – Should you buy now and pay later? – Official overview of how BNPL works, risks, and when it might make sense.
- CFPB – What is a Buy Now, Pay Later (BNPL) loan? – Definitions and key features of common pay-in-4 style plans.
- FTC – Want to buy now but pay later? Read this first – Consumer protection tips and fee pitfalls to watch for.
- Investopedia – Buy now, pay later: convenient payment option or a debt trap? – Deep dive into BNPL pros, cons, and how to compare with credit cards.