What does the Buy Now Pay Later Calculator do?

Calculate BNPL instalment costs for Klarna, Clearpay and custom plans. See the true cost and late fee risks. All calculations are performed in your browser using official UK rates and thresholds.

Does this use current UK interest rates?

You can enter any interest rate to model different scenarios. The Bank of England base rate and FCA guidelines influence typical lending rates available in the UK market.

Should I get professional debt advice?

If you are struggling with debt, free professional advice is available from StepChange (0800 138 1111), Citizens Advice, and the National Debtline (0808 808 4000). This calculator provides estimates only.

Buy Now Pay Later Calculator

Calculate BNPL instalment costs for Klarna, Clearpay and custom plans. See the true cost and late fee risks.

Last updated: April 2026 · Source: FCA — Buy now, pay later

Purchase Amount

BNPL Provider

3 Payments of

£66.67

Total Paid

£200.00

Interest

FREE

Late Fee Risk

£6/miss

BNPL can affect your credit score. Missing payments incurs late fees (~£6) and can be reported to credit agencies. Always ensure you can afford all instalments before committing.

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

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. However, late payment fees typically range from £6 to £12 per missed instalment, and repeated use can lead to overcommitment across multiple agreements.

From 2025, BNPL providers are expected to be regulated by the FCA, meaning affordability checks and clearer disclosures will become mandatory. BNPL usage is also increasingly visible on credit files, which means missed payments may affect your credit score and future borrowing ability.

This calculator shows the true cost of a BNPL purchase including any late fees. Enter the purchase price, number of instalments and any fees to see the total you actually pay. It also highlights the monthly budget impact of stacking multiple BNPL agreements.

Example: £300 purchase with Pay in 3

Three payments of £100 over 6 weeks — no interest if on time
One missed payment with £6 late fee: total cost £306
Two missed payments: total cost £312
Effective cost of late fees as an interest rate: approx. 24% APR equivalent

Source: FCA — Buy now, pay later

Frequently Asked Questions

What does the Buy Now Pay Later Calculator do?: Calculate BNPL instalment costs for Klarna, Clearpay and custom plans. See the true cost and late fee risks. All calculations are performed in your browser using official UK rates and thresholds.
Does this use current UK interest rates?: You can enter any interest rate to model different scenarios. The Bank of England base rate and FCA guidelines influence typical lending rates available in the UK market.
Should I get professional debt advice?: If you are struggling with debt, free professional advice is available from StepChange (0800 138 1111), Citizens Advice, and the National Debtline (0808 808 4000). This calculator provides estimates only.