Free tool
Flat rate vs interchange plus calculator
Interchange plus is cheaper above a break-even turnover and the flat rate is cheaper below it. Enter the merchant's figures to find where the two cross.
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How this tool works
How do you use it?
- Enter the merchant's monthly card turnover and average transaction value.
- Enter the flat rate offered, then the interchange plus offer: the provider's markup, its fee per transaction and its monthly fee.
- Enter the merchant's bank and card network costs (interchange and scheme fees). Use the figure from their statement, or an estimate if you are comparing blind.
The formulaBreak-even turnover = monthly fee / ((flat rate minus interchange minus markup) / 100 minus per-transaction fee / average transaction value)
What does a worked example look like?
The tool opens with this example, in pounds.
- Monthly turnover
- £20,000
- Average transaction
- £25
- Flat rate
- 1.50%
- Bank and card network costs
- 0.70%
- Provider's markup
- 0.30%
- Fee per transaction
- £0.05
- Monthly fee
- £20
- Flat rate: the merchant would pay
- £300.00 a month
- Interchange plus: the merchant would pay
- £260.00 a month
- Interchange plus is cheaper
- Saves £40.00 a month
- Where the two cost the same
- £6,667 of card turnover a month
Which mistakes should you avoid?
- Guessing the interchange figure and presenting the answer as exact. Use a real statement where you can.
- Forgetting the per-transaction fee, which can wipe out the saving on small payments.
- Ignoring the merchant's quiet months. Test the plan on their weakest month, not only their best.
Frequently asked questions
What is the break-even point?
The monthly turnover where both pricing models cost the merchant the same. Above it, the model with the lower percentage and a monthly fee wins.
Why does average transaction value matter?
A per-transaction fee is a bigger share of a small payment. With a low average transaction value, interchange plus can lose even at high turnover.
Where do I find the merchant's interchange and scheme fees?
On an interchange plus statement they are shown as lines. On a blended or flat statement they are hidden, so ask the provider or use an estimate.
Is this a quote?
No. It is an illustration based on the numbers you enter. Always get the offer in writing from the provider.
These tools give illustrations based on the numbers you enter. They are not quotes, financial advice or legal advice. Check any offer with the provider in writing.
Want the whole statement worked out?
The free calculator handles every card type, every fee and a side-by-side with an offer, and builds a quote PDF.