Methodology

What this calculator does

This calculator takes a purchase amount, a specific Buy Now Pay Later plan, and optional missed-payment information, then computes three things: the total amount you'll pay, two different annual percentage rate figures for that plan, and a side-by-side comparison to paying the same purchase on a credit card over the same time horizon. It uses fee data from each provider's publicly published schedule — not individually negotiated or checkout-specific rates.

The two APR figures, explained

The calculator displays two APR figures side by side because they measure slightly different things and are used in different contexts.

Simple APR uses the annualized fee rate formula:

Simple APR = (total cost above purchase ÷ purchase amount) × (365 ÷ loan term in days) × 100

"Total cost above purchase" includes all fees and interest charges above the original purchase price. This is the method used by most popular BNPL calculators and financial comparison tools. It answers the question: if you express all extra costs as a yearly rate, what is it?

Regulatory APR (TILA) uses the actuarial method defined in 12 CFR §1026 Appendix J — "Annual Percentage Rate Computations for Closed-End Credit Transactions." This is the legally required disclosure standard in the United States for closed-end credit. It solves for the daily periodic rate r such that the present value of all scheduled payments equals the amount financed:

Σ (payment_k ÷ (1 + r)^days_k) = purchase amount

The annual rate is then r × 365 × 100. This computation uses Newton-Raphson iteration with a convergence tolerance of 0.0001 percentage points.

Both figures are shown because they can diverge noticeably on short-duration plans with flat fees, and showing only one would give an incomplete picture.

Assumptions made

The credit card comparison assumes you carry the balance at the specified APR and make equal monthly payments over the same number of months as the BNPL plan's term (rounded up to the nearest month). It uses standard amortization. It does not assume minimum payments, cash-advance rates, annual fees, or rewards.

For plans with a variable interest rate range (where the provider publishes a minimum and maximum APR but sets your specific rate at checkout based on creditworthiness), the calculator uses the midpoint of the published range. Results for variable-rate plans are flagged with a note indicating the estimate. Your actual rate will differ.

Missed payment fees are applied starting from the second scheduled payment (index 1). The first payment is always assumed to be on time. Each missed payment adds the provider's published flat late fee to that installment. The calculator does not model grace periods or fee caps beyond what is noted in the provider data.

What the calculator does not do

This calculator does not predict your individual approval terms. Actual interest rates and credit limits depend on a soft or hard credit check at checkout and vary by person. It does not factor in the credit-score impact of missed payments or hard inquiries. It does not assess whether any specific purchase is a sound financial decision. It does not model provider-specific payment extensions, hardship programs, or late-fee waivers that may be available but are not part of the published fee schedule.

Limits of accuracy

Provider fee structures change. Every entry in this calculator includes a "last verified" date reflecting when the fee data was confirmed against the provider's official published schedule. Fee data is reviewed periodically — not in real time. Before completing any purchase, verify the applicable fees directly on the provider's website or in the terms presented at checkout. A link to each provider's official fee page is displayed alongside calculator results. For the full provider source table and update policy, see data sources.