Buy Now Pay Later Calculator

Buy Now Pay Later (BNPL) services like Klarna, Clearpay and PayPal Pay in 3 let you spread payments over weeks or months, often interest-free. The typical shape is 3-4 instalments at 0% provided every payment lands on time. Late fees are typically £5 or £6 per missed instalment, and Clearpay adds a second £6 if the payment is still unpaid 7 days later. Repeated use can lead to overcommitment across multiple agreements. Take-up is broad, with FCA figures putting BNPL use at 26% of UK adults in 2024 and an estimated £6+ billion outstanding.

What the headline misses is what happens when a payment slips. Interest-free plans charge flat late fees rather than interest, and Clearpay caps its total late fees at 25% of the order value or £24, whichever is lower. Longer financing plans do charge interest, so check the APR before you sign. On a £300 Pay in 3 purchase, split into three monthly payments of £100 over about 60 days, one missed payment with a £6 fee takes the cost to £306 and two missed payments take it to £312.

This calculator shows the true cost of a BNPL purchase including any late fees. Enter the purchase price, the plan type, the late fee and any missed payments to see the total you actually pay, then add what you already pay each month on other BNPL plans to see your combined monthly commitment. That stacking is the real risk: because each plan is small and separately scheduled, the combined commitment is easy to lose track of.

Since 15 July 2026 the FCA has regulated BNPL, formally deferred payment credit, for agreements made from that date where the lender and the retailer are different businesses. Lenders must check you can afford to repay before you sign, tell you upfront how much you are borrowing, when the payments fall due and what any late fee will be, and support you if you struggle to pay. You can take a complaint to the Financial Ombudsman Service. Agreements made before 15 July 2026 stay unregulated, so older plans do not carry these protections.

BNPL usage is also increasingly visible on credit files, which means missed payments may affect your credit score and future borrowing ability. Klarna has shared Pay in 3 and Pay in 30 days data with Experian and TransUnion since June 2022, on-time payments as well as late ones, and other providers may report missed payments too. Hard searches from several credit applications are visible to mortgage lenders. If a mortgage application is on the horizon, check your report with Experian, Equifax or TransUnion, each of which offers a free version, around 6 months beforehand.

As a product, BNPL suits a planned purchase you can comfortably clear over 4-8 weeks, a large appliance or furniture buy where the retailer offers no 0% credit, or spreading Christmas and birthday spending. It compares poorly with a 0% credit card, which buys 24+ months rather than 4 instalments, and poorly with simply buying within budget. Studies show people spend 30-50% more on BNPL than with cash, with an average BNPL transaction of £75-£150 against £55-£95 for the same person paying outright. Section 75 of the Consumer Credit Act, which makes the lender jointly liable if something goes wrong with a single item costing over £100 and up to £30,000, applies to regulated BNPL agreements made from 15 July 2026, but not to older ones.