Buy now pay later (BNPL) true-cost calculator

What this tool does

Split payments feel free because each instalment is small and the app never adds them up for you. This tool does. List every buy-now-pay-later plan you have running, with its price, how many instalments it splits into, and how often they fall due. It works out what each one costs per instalment and in full, then stacks them into the one number the checkout hides: what all your splits together commit you to each month. If you want to see what a missed payment does, type the late fee you would face and the tool shows the effective annual rate that nominally free split would then carry.

How the maths works

Each split is broken into equal instalments, the price divided by the number of instalments, and converted to a monthly figure by how often you pay: weekly counts 52 times a year, every two weeks 26, monthly 12. That gives what each plan costs a month while it runs, and the stacked total adds those up across your active splits.

The effective annual rate, the APR, is worked out with the standard present-value method used across Europe to annualise the cost of credit: it finds the single yearly rate at which what you get today equals what you pay back over time. It is our own illustration of your figures, not a rate a lender has quoted you. Nor is it the official APR a lender must publish: that assumes you keep to the plan, so for a genuinely interest-free split it is 0%. A late fee is what tips it, spread over a short repayment window, and the tool charges the fee at the final instalment, the most cautious timing.

The late fee is your own assumption, not a Money Owl figure and not any provider's rate; the tool names and recommends no product. Buy-now-pay-later is being brought under Europe's consumer-credit rules, though some short, interest-free store plans stay outside them. Every figure here is your own: your prices, your instalments, your cadences. Nothing is saved; reload and you start fresh. This tool is educational, not financial advice.

When to use it

Before you tap the split option at a checkout, or whenever you already have a few plans running and cannot remember what they add up to. Put each one in, look at the stacked monthly figure, and decide whether that commitment is one you would sign if the checkout had shown it as a single number. If you tend to miss the odd payment, add the late fee you would face and see what the free split actually costs. There is no target number and no regulator rule here; the only number that matters is whether the stack is bigger than you thought.