The cheapest processor depends on three numbers you already have.
Monthly volume, average ticket and card mix decide this, and they decide it differently for every business. What follows is the actual arithmetic, the published figures to run it against, and where the answer tends to land.
What this page settles.
Three questions, in the order most people ask them.
Why there is no single answer
Every page that names a single cheapest processor is either guessing or selling, and usually both.
The reason is structural. Interchange is 70% to 80% of what you pay, it varies by card type, and the cards your customers carry are not the cards somebody else’s customers carry. A coffee counter whose customers mostly tap regulated debit cards and a jewellery shop whose customers mostly use premium rewards credit cards are paying wildly different interchange on identical volume. A flat rate charges both the same and keeps the difference. What interchange is.
On top of that, the fixed per-transaction fee matters enormously at small ticket sizes and almost not at all at large ones. A 15¢ per-item is 1.5% of a $10 sale and 0.02% of a $800 one.
So “who is cheapest” is the wrong question and “cheapest for what” is the right one. The good news is that the answer is arithmetic rather than opinion, and you can do it in ten minutes.
The three numbers
Get these before reading any further. All three come off one month of statements.
Monthly card volume. Total card sales for a month. This decides which pricing model wins.
Average ticket. Card volume divided by the number of card transactions. This decides how much the per-item fee matters. Under $20 it dominates; over $100 it is noise.
Debit share. Roughly what proportion of your volume is debit rather than credit. Most statements show this; if yours does not, your processor can tell you. Regulated debit interchange is capped by law and low, which means a flat rate is at its least generous on a debit-heavy business. Debit versus credit cost.
A fourth, if it applies: what share is keyed or online, because card-not-present interchange runs roughly 0.3% to 0.5% above the card-present equivalent and the published rates differ sharply by channel. Selling online.
Where the crossover actually falls
The structural question is flat rate against interchange-plus, and it has a reasonably well-behaved answer.
Card-present interchange plus assessments for a mixed consumer card base typically lands somewhere around 1.9% to 2.1% all in. A flat rate of 2.6% is therefore roughly 0.5% to 0.7% above what the networks charge. An interchange-plus margin of 0.40% plus a few cents is well below that.
So the crossover is wherever the interchange-plus provider’s fixed costs are covered by the margin saving.
Against a provider with no monthly fee at all — Helcim publishes 0.40% + 8¢ with nothing monthly — the crossover is almost immediate. There is no fixed cost to cover, so interchange-plus wins from a few thousand a month, and the only reason to stay on a flat rate below that is that the difference is too small to be worth an afternoon.
Against a provider with a small monthly fee — Dharma publishes 0.15% + $0.08 with $20 a month — the crossover against a flat rate is well under $5,000 a month.
Against a subscription — Stax publishes $99 a month with no percentage — the crossover against a flat 2.6% is around $12,000 to $15,000 a month.
The practical summary: below about $10,000 a month, the difference is small enough that convenience and software should decide. Above it, interchange-plus is cheaper and keeps pulling away. Above $50,000 a month, staying on a flat rate is costing hundreds a month.
The cheapest published options, by size
Based on published figures read on 2026-10-08. These are starting points, not recommendations for your business, and three of them are competitors of ours.
Taking a few hundred a week, in person, no software needed. PayPal’s 2.29% + 9¢ card present is the lowest published in-person rate here, and there is no monthly fee. SumUp at 2.6% + 10¢ is close and simpler.
A small shop or salon that wants software too. Square’s free tier at 2.6% + 15¢ with a genuinely capable till app at $0 a month is hard to beat on total cost at this size, because the software would otherwise cost something.
$10,000 to $50,000 a month. Helcim at interchange + 0.40% + 8¢ with no monthly fee, or Dharma at interchange + 0.15% + $0.08 with $20 a month. Dharma is cheaper above roughly $8,000 a month. Both publish, both have unusually short fee lists, and both will be considerably cheaper than any flat rate in this range.
$50,000 a month and up. Stax’s subscription model, Dharma’s high-volume schedule at 0.10% + $0.08 above $100,000 a month, or a negotiated interchange-plus arrangement through an ISO — which above a few hundred thousand a month can go below any published schedule.
Online, at any size. The channel costs more and the published rates reflect it. Stripe at 2.9% + 30¢ is the benchmark; the surcharges for international cards and currency conversion are where the real variance is. Above roughly $40,000 to $60,000 a month online, interchange-plus wins here too.
Anything bundled with a point-of-sale system — Toast, Clover, Lightspeed, SpotOn, NRS — is not competing on processing cost and should not be chosen on it. You are buying the system, and the processing comes attached. Choosing a retail POS.
What makes a cheap deal expensive later
Four things, and they outweigh rate differences routinely.
An equipment lease. A $79 a month non-cancellable lease over 48 months is $3,792 for a terminal worth a few hundred dollars, it is usually with a third-party finance company, and it does not end when you leave the processor. This single clause has made more “cheap” deals expensive than every rate in this article combined. Equipment lease fees.
A term with liquidated damages. Not a flat termination fee — a formula based on your average monthly fees times the months remaining. On a merchant with real volume and two years left, thousands. Early termination fees.
A monthly minimum you miss in a quiet month, or a minimum processing commitment, which is worse. Monthly minimum and small fees.
A PCI non-compliance fee that appears because nobody filled in the questionnaire. $20 to $40 a month, pure waste, removable in under an hour. PCI non-compliance fee.
A rate half a percent better than the alternative saves $150 a month on $30,000. Any one of the four above can cost more than that.
How to settle it in ten minutes
Work out your current effective rate. Total fees for a month divided by total card volume. That single number is what everything else compares to. The calculator does it from two figures, and what an effective rate is explains the answer.
Work out your average ticket. Volume divided by transaction count.
Price two published alternatives at your own numbers. Take interchange + 0.40% + 8¢ and add a reasonable interchange assumption for your card mix. Take a flat 2.6% + 15¢. Compare both to what you pay now.
Add every monthly fee to both sides. This is the step people skip and it reverses the answer more often than any other.
Then decide whether the difference is worth the move. Under $50 a month, probably not. Over $150 a month, almost certainly. In between, it depends how much the hardware and the admin will cost you.
What we charge
Interchange + 0.50% + 10¢ in person, interchange + 0.75% + 25¢ keyed, with no contract, no monthly fee, no monthly minimum and no termination fee.
We are not the cheapest published margin on this page and we have not pretended to be — Dharma’s 0.15% is lower and it is public. What we do is read your actual statement and tell you what you actually pay, which is the step everything on this page depends on, and we do it whether or not you move. If one of the options above is better for you, we would rather say so than win an account you leave in six months.
While we are on the subject
Is Square the cheapest?
Below roughly $12,000 a month in card volume, often effectively yes once you count the absence of monthly fees and the time saved. Above that, no — a flat rate stops being competitive and keeps getting less so.
Is interchange-plus always cheaper?
Not at low volume, where a small fixed fee or a monthly minimum can outweigh the margin saving. Above roughly $12,000 a month it almost always is.
Can I get a rate below the published ones?
At high volume, yes — negotiated interchange-plus through an ISO can go below the published schedules. Below a few hundred thousand a month, the published ones are competitive.
Why does nobody just say who is cheapest?
Because the answer genuinely differs by business. A debit-heavy coffee counter and a premium-card jewellery shop at the same volume have different cheapest providers.