BNPL Calculator
Work out the real cost of a buy now pay later plan including late fees, and compare it against paying outright or using a credit card.
Last reviewed by the Radiatus Cloud team
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Interest-free is not cost-free
Most BNPL plans genuinely charge no interest if every instalment is paid on time. The revenue comes from two places: merchant fees of typically 2 to 8 percent, which are built into prices everyone pays, and late fees charged to users who miss a payment. The advertised zero percent is real for the disciplined and irrelevant for anyone who slips.
Late fees are enormous relative to the amount
A fixed late fee of 6 or 8 on a 40 instalment is an effective rate far above any credit card, because the fee does not scale down with the small balance. Two missed payments on a modest purchase can add 20 to 40 percent to its cost. Judge BNPL on the fee structure and your confidence in the payment dates, not on the headline rate.
Stacking is the real hazard
The mechanism that causes harm is not one plan but several. Each is individually small and easily affordable, and because approval is instant and often does not involve a hard credit check, there is no natural brake. Four concurrent plans produce a stream of payments on different dates from different providers with no single view of the total. Regulatory reviews in several countries have identified this as the main driver of BNPL-related arrears.
Credit reporting is inconsistent
Some providers now report to credit bureaux and some do not, and this is changing. Missed payments increasingly appear on credit files, while on-time payments often do not, giving asymmetric downside. Some mortgage underwriters treat active BNPL commitments as a negative signal about cash flow management regardless of payment history.
When it makes sense
Spreading a genuinely necessary purchase you could afford outright, to smooth cash flow across a month, with the payment dates diarised. It stops making sense when it is what makes the purchase possible at all. The honest test is whether you would buy the item if you had to pay the full amount today. If the answer is no, the instalment plan is not helping you afford it, it is helping you overspend.
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Frequently Asked Questions
Is buy now pay later really interest-free?
Usually yes if every instalment is paid on time. Providers earn from merchant fees of 2 to 8 percent, built into prices, and from late fees. The zero percent is real for the disciplined and meaningless for anyone who misses a date.
How bad are the late fees?
Severe relative to the amount. A fixed fee of 6 or 8 on a 40 instalment is an effective rate far above any credit card, because it does not scale with the small balance. Two misses can add 20 to 40 percent.
Does BNPL affect my credit score?
Increasingly, and asymmetrically. Missed payments are reported by more providers over time while on-time payments often are not. Some mortgage underwriters treat active BNPL commitments as a negative cash-flow signal regardless.
What is the main risk?
Stacking several plans at once. Each is individually affordable and approval is instant with no hard check, so nothing limits accumulation. Regulators in several countries identify this as the principal cause of BNPL arrears.
When is BNPL a reasonable choice?
For a necessary purchase you could afford outright, to smooth cash flow within a month, with dates diarised. If you would not buy the item at full price today, the plan is enabling overspending rather than affordability.
Privacy & Security
Runs entirely in your browser. Purchase and payment details are not uploaded.
How to Use
Enter the purchase amount, upfront payment, plan duration, fees and a comparison APR to estimate total BNPL cost versus an alternative credit option.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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