BNPL vs Credit Card Calculator

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How this BNPL vs credit card calculator works

This calculator compares the cost of using a buy now, pay later (BNPL) plan with paying for the same purchase on a credit card over a chosen number of months. It focuses on the total dollars you actually pay: monthly payment, total paid, and total interest or fees for each option.

To use it, enter:

Purchase price – the item or cart total you want to finance.
BNPL fee or interest (%) – a one-time percentage fee or interest rate the BNPL plan charges on the purchase amount.
BNPL repayment months – how many months you will take to pay off the BNPL plan.
Credit card APR (%) – the annual percentage rate on your credit card.
Months to pay card – how many months you plan to take to fully pay off this purchase on the card.

When you hit the calculate button, the tool estimates:

Monthly payment for the BNPL plan and for the credit card.
Total amount paid under each option.
Total interest and fees paid under each option.
Which option is cheaper in total cost, based on your inputs.

Formulas used in the calculator

BNPL cost formula (flat fee or interest)

In this calculator, BNPL is modeled as a simple percentage fee (or interest) applied once to the purchase price.

Let:

P = purchase price
f = BNPL fee rate as a decimal (for example, 6% = 0.06)
n = number of months in the BNPL plan

Total amount owed under BNPL:

Total = P \times (1 + f)

Monthly BNPL payment:

Payment = \frac{P \times (1 + f)}{n}

BNPL fees paid are simply:

BNPL fees = P × f

Credit card amortization formula

The credit card side is modeled as a standard fixed-payment loan over a set number of months, using the card’s APR.

Let:

P = purchase price (amount charged to the card)
r = annual percentage rate (APR) as a decimal (for example, 24% = 0.24)
i = monthly interest rate = r / 12
m = number of months you plan to take to pay off the balance

Monthly credit card payment (amortized):

M = \frac{P \times i \times {(1 + i)}^{m}}{{(1 + i)}^{m} - 1}

Total amount paid on the credit card is M × m, and total interest paid is:

Card interest = (M × m) − P

These are standard loan formulas used in many financial calculators and educational resources on loan amortization.

Interpreting your results

After you enter your purchase details and run the numbers, the calculator shows a side-by-side summary. Here is how to read it:

Monthly payment – helps you check affordability in your budget. A lower monthly payment is easier to fit in, but may or may not mean a lower total cost.
Total paid – the full amount you will have paid after all installments or card payments, including interest and fees. This is the best figure for comparing overall cost.
Interest/fees – isolates the cost of financing, separate from the item price. This is the extra money you pay just for the ability to spread payments out.
Cheaper option – highlights which path costs less in total dollars, given your inputs. You can change the months or rates to see how the cheaper option can flip.

The default numbers in the comparison table (if any appear before you calculate) are only placeholders. Once you click the calculate button, the table updates with values from your specific scenario.

Worked example: when BNPL costs more

Imagine a $600 purchase. You can choose between:

A BNPL plan charging a 5% fee, repaid over 6 months.
A credit card with a 24% APR, repaid over 6 months.

BNPL calculation

Purchase price P = 600, fee rate f = 0.05, term n = 6 months.

Total BNPL amount = 600 × (1 + 0.05) = 600 × 1.05 = $630.
Monthly BNPL payment = 630 ÷ 6 = $105.
BNPL fees paid = 600 × 0.05 = $30.

Credit card calculation

Purchase price P = 600, APR r = 0.24, monthly rate i = 0.24 ÷ 12 = 0.02 (2%), term m = 6 months.

Monthly payment:

M = 600 × 0.02 × (1.02^6) / (1.02^6 − 1)

First calculate the growth factor:

1.02^6 ≈ 1.1262

Then:

Numerator ≈ 600 × 0.02 × 1.1262 ≈ 600 × 0.022524 ≈ 13.51
Denominator ≈ 1.1262 − 1 = 0.1262
M ≈ 13.51 ÷ 0.1262 ≈ 107.05

So:

Monthly credit card payment ≈ $107.05.
Total paid on card ≈ 107.05 × 6 ≈ $642.30.
Total interest ≈ 642.30 − 600 = $42.30.

In this example, the BNPL plan is cheaper on total cost ($30 of fees) than the card ($42.30 of interest), and it also has a slightly lower total paid ($630 vs $642.30). However, the credit card’s monthly payment is a little higher, which may or may not matter depending on your budget.

Second example: when a credit card can win

Now imagine the same $600 purchase, but your credit card has a 0% intro APR for 6 months, and the BNPL plan still charges a 5% fee over 6 months.

BNPL

Total BNPL amount = $630.
Monthly BNPL payment = $105.
BNPL fees = $30.

Credit card (0% intro APR for 6 months)

APR r = 0.00 during the promo period, so if you pay the balance off in 6 months:

Monthly payment = 600 ÷ 6 = $100.
Total paid = $600.
Total interest = $0.

In this scenario, the credit card is clearly cheaper because the 0% intro APR lets you spread the purchase over 6 months with no interest, while the BNPL plan still charges a 5% fee.

BNPL vs credit card: side-by-side comparison

The table below summarizes typical differences between BNPL plans and credit cards. Your specific terms may vary, so always check your actual agreement.

Feature	BNPL plan (as modeled here)	Credit card (as modeled here)
How cost is calculated	One-time percentage fee or interest on the purchase price.	Ongoing interest based on APR, compounded monthly.
Payment structure	Fixed number of installments over a set term.	Fixed monthly payment over your chosen payoff period.
Typical term length	Short, often 3–12 months.	Flexible; you choose months to pay in the calculator.
Promotional offers	Sometimes 0% fee if paid on time.	Often 0% intro APR for a limited period on new purchases or balance transfers.
Late fees and penalties	Many BNPL providers charge late fees or may restrict future use.	Late fees and penalty APRs may apply if you miss payments.
Rewards and cashback	Some BNPL apps offer perks, but many do not.	Many cards offer cashback, points, or miles, which can offset costs.
Impact on credit	Reporting varies by provider; may be limited or evolving.	Most cards report monthly to credit bureaus and affect your credit history.

Limitations and assumptions of this calculator

This tool is designed to give clear, comparable estimates, not to model every detail of real-world financing. Important assumptions include:

BNPL is a simple percentage fee applied once to the purchase price. It does not model compounding interest, tiered fees, or fees that change over time.
No late fees or penalties are included for either BNPL or the credit card. In reality, missing payments can significantly increase your total cost.
No new spending on the card is assumed. The calculator treats the card balance as a single purchase that you pay off over the months you enter.
APR stays constant for the entire payoff period. It does not model teaser rates that later increase, or penalty APRs.
0% intro APR offers are not modeled automatically. To approximate one, you can enter 0% APR and set the months to pay card equal to the promo period.
Rewards and cashback are not included in the cost comparison. If your card offers rewards, your effective net cost may be lower.
Taxes and other merchant fees are not modeled separately. You can include them in the purchase price if you want them reflected.
Results are estimates only and may differ from the amounts shown in your provider or card issuer’s statements.

Always check the exact terms from your BNPL provider and credit card issuer before making a decision. This calculator is for educational and planning purposes only and is not financial advice.

Common questions about BNPL vs credit cards

Is BNPL always cheaper than using a credit card?

No. BNPL can be cheaper when the fee is low and your card APR is high, but a low-APR card or a 0% intro offer can easily beat a BNPL plan that charges fees.

How do late fees affect the comparison?

Late fees can quickly erase any savings from either option. BNPL providers and card issuers often charge extra fees or raise rates if you miss payments. The calculator does not include these, so staying on time is crucial.

What if my credit card has a 0% intro APR?

You can approximate a 0% intro APR by entering 0% APR and a months-to-pay value that matches the promo period. Just be sure you can clear the balance before the intro rate expires.

Does this calculator include rewards or cashback?

No. Rewards, points, and cashback are not factored in. If your card offers strong rewards, your net cost may be lower than shown.

How should I choose between BNPL and a credit card?

Compare total cost, monthly payment affordability, risk of late fees, and any rewards or protections you value. Then choose the option that is both affordable and aligns with your financial habits.