---
title: "Buy Now, Pay Later True Cost Calculator | Honest Interest"
description: "What a pay-in-4 or monthly BNPL plan really costs with fees and late fees, the yearly rate those fees equal, and how carrying it on a card compares."
url: https://honestinterest.bond/buy-now-pay-later-calculator/
---

Calculator 05 · Payment plans

# Buy now, pay later: the true cost

Pay-in-4 is interest-free when every payment lands on time. Add a late fee, a checkout fee or a longer plan with interest, and the cost becomes a rate. Here is that rate.

**Educational use only — not financial advice.** No lender or plan is recommended here. Terms, fees and caps vary between lenders and change over time.

## How the cost is worked out

A pay-in-4 plan splits the price into four equal parts: one at checkout, then one every two weeks, so the last is paid six weeks later. That is how the CFPB's 2022 market report describes the typical plan. Monthly plans spread payments over months and may charge interest.

The calculator lists every payment with its fees, then finds the yearly rate those extra dollars amount to, using the actuarial method Regulation Z's Appendix J sets out for APRs: the rate at which the payments, discounted back to checkout, equal what you actually borrowed. On a $400 pay-in-4 purchase you borrow $300 after the first payment, and a single $10 late fee works out to about 43.8% a year.

A lender's disclosed APR leaves late fees out, because late fees are not finance charges under Regulation Z. Counting them shows what paying late costs. The CFPB reported that 10.5% of BNPL users were charged at least one late fee in 2021, up from 7.8% in 2020.

## Sources

- Consumer Financial Protection Bureau, [Buy Now, Pay Later: Market trends and consumer impacts](https://www.consumerfinance.gov/data-research/research-reports/buy-now-pay-later-market-trends-and-consumer-impacts/) (September 15, 2022): how pay-in-4 plans are structured.
- Consumer Financial Protection Bureau, [CFPB Study Details the Rapid Growth of "Buy Now, Pay Later" Lending](https://www.consumerfinance.gov/about-us/newsroom/cfpb-study-details-the-rapid-growth-of-buy-now-pay-later-lending/) (September 15, 2022): the late fee figures.
- Consumer Financial Protection Bureau, [Consumer Use of Buy Now, Pay Later and Other Unsecured Debt](https://www.consumerfinance.gov/data-research/research-reports/consumer-use-of-buy-now-pay-later-and-other-unsecured-debt/) (January 13, 2025): reporting of BNPL loans to credit bureaus.
- Consumer Financial Protection Bureau, Regulation Z, [Appendix J to Part 1026 — Annual Percentage Rate Computations for Closed-End Credit Transactions](https://www.consumerfinance.gov/rules-policy/regulations/1026/j/): the actuarial method and unit periods.
- Consumer Financial Protection Bureau, Regulation Z, [§ 1026.4 Finance charge](https://www.consumerfinance.gov/rules-policy/regulations/1026/4/): charges for actual, unanticipated late payment are excluded from the finance charge (paragraph (c)(2)).
- Consumer Financial Protection Bureau, [What is a grace period for a credit card?](https://www.consumerfinance.gov/ask-cfpb/what-is-a-grace-period-for-a-credit-card-en-47/)

## Questions

**Why compare with a credit card?**

Because carrying a purchase on a card is the usual alternative. The card line assumes you pay the same share of the price on the same dates and carry the rest, with interest charged daily at the APR you enter. If you would pay the whole statement by the due date, a card's grace period usually means no interest at all.

**Do BNPL loans show up on credit reports?**

The CFPB's January 2025 study notes that BNPL lenders have generally not reported these loans to the nationwide consumer reporting companies. Practices can change, so check your lender's terms.

**How are late payments counted?**

Each late payment adds one late fee, starting with the first payment after checkout. The calculator adds no other penalty, because plans differ; enter the plan's own fee and, for monthly plans, its own interest rate.