Flat rate vs interchange-plus calculator
Enter your monthly card sales, average sale and debit share to see what a flat rate costs you next to an interchange-plus estimate, in dollars a month and a year.
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Example numbers. Change them to match last month's processing statement.
Card sales divided by the number of card transactions.
The rest is credit. Not sure? Leave it.
The rest is online or keyed in.
Stripe's published online price is 2.9% + 30¢. Its in-person price is 2.7% + 5¢.
The flat rate costs you more by
$3,967 to $6,012 a year
About $331 to $501 a month
- Flat rate at 2.9% + 30¢
- $1,400 a month$16,800 a year, 3.50%
- Interchange-plus estimate
- $899 to $1,069 a month$10,788 to $12,833 a year
- Card transactions a month
- 800
Your volume and flat-rate fees carry into the quiz, already filled in.
The interchange-plus estimate uses published Visa interchange and one published interchange-plus price, before card-network fees. The range runs from basic cards to top rewards cards. Not a quote.
How the math works
- Transactions = card sales / average sale. $40,000 at a $50 average sale is 800 sales.
- Flat rate cost = card sales x the percent, plus the number of sales x the per-sale fee. At 2.9% + 30¢ that is $1,160 + $240 = $1,400 a month.
- Interchange-plus estimate: credit sales are priced with Visa's published U.S. interchange table, dated April 18, 2026, from the basic card to the top rewards card. Debit is priced at Visa's regulated debit rate, 0.05% + 22 cents including the fraud-prevention cent. Then one processor's published markup is added: 8 cents per in-person sale, 15 cents per online sale, and a monthly fee of $99 up to $150,000 a year in sales, $139 up to $250,000, and from $199 above that (Stax, Oct 2026).
- Difference = flat rate cost minus the interchange-plus estimate, each month, then x 12 for the year.
The default flat rate is Stripe's published online price, so the in-person share starts at 0%. If you take cards in person, raise that share and enter your own flat rate; Stripe lists 2.7% + 5¢ in person. The estimate uses Visa's table for every card brand and leaves out card-network fees, so treat it as a guide, not a quote.
To test your own statement against the same estimate, use the processing fee analyzer.
Our take
Before you switch, ask any interchange-plus quote for its markup per sale, its percent markup if any, and every monthly fee in writing. The comparison only holds if those numbers are on paper.
Common questions
Sources
- Stripe, Pricing ("2.9% + 30¢ per successful transaction for domestic cards" online; "2.7% + 5¢" in person), accessed Oct 20, 2026
- Visa, Visa USA Interchange Reimbursement Fees (rates effective April 18, 2026), accessed Oct 20, 2026
- Federal Reserve Board, Regulation II (Debit Card Interchange Fees and Routing), accessed Oct 20, 2026
- Stax, Pricing (published interchange-plus subscription price used as the benchmark), accessed Oct 20, 2026