Payment Processing Fee Math: How to Read Stripe & PayPal Fees and Gross-Up to Net Your Target

The first time a Stripe payout landed in my account, the number was wrong. I had charged a client $100 and $96.80 showed up. Not a bug — just the processing fee doing exactly what it always does, quietly taking its cut before the money reaches you. If you sell anything online, that gap between what you charge and what you keep is worth understanding down to the cent, because it compounds across every order.

This guide walks through how card fees actually work, the one formula that lets you charge so you receive a clean amount, and the small mistakes that cost real money. You can follow along with the payment processing fee calculator and check each number as you go.

The percent-plus-fixed model

Almost every card processor charges fees the same way: a percentage of the sale plus a fixed amount per transaction. Stripe's standard US rate is 2.9% + $0.30. PayPal sits around 3.49% + $0.49 for many flows. Square matches Stripe at 2.9% + $0.30. The percentage covers the processor's cost as a fraction of risk and volume; the fixed fee covers the flat cost of moving a single transaction, regardless of size.

So the fee on any charge is:

fee = amount × rate + fixed

For a $100 charge at Stripe's rate:

fee = 100 × 0.029 + 0.30 = 2.90 + 0.30 = 3.20
net = 100 − 3.20 = 96.80

That is the $96.80 from my payout. Nothing mysterious — the math is just two terms, one that scales with the sale and one that does not.

Why the effective rate beats the sticker rate

The headline "2.9%" is honest only on mid-sized charges. Because the fixed fee never moves, it dominates on small ones. The number that tells you the real story is the effective rate:

effective rate = fee ÷ amount

On a $100 charge, the effective rate is 3.20 ÷ 100 = 3.2%, barely above the sticker. On a $3 charge it is a different world:

fee = 3 × 0.029 + 0.30 = 0.087 + 0.30 = 0.387 ≈ 0.39
effective rate = 0.39 ÷ 3 ≈ 13%

A $0.30 fee on a $3 sale is a 13% bite, not 2.9%. This is why "it's only 2.9%" is a trap for anyone selling cheap digital goods, tips, or micro-subscriptions. If your average ticket is small, bundle items into larger orders or set a minimum, and watch the effective rate fall back toward the headline as the amount grows.

The gross-up: charge so you receive the full amount

Here is the question that trips people up. You need exactly $100 to land in your account. How much do you charge?

The wrong instinct is to add the percentage: $100 + 2.9% = $102.90. But the fee is then charged on $102.90, not $100, so you net $102.90 − (102.90 × 0.029 + 0.30) = $99.62. Still short. You undershot because the percentage takes a second bite on the amount you added.

The correct move is a gross-up. Start from what you receive:

net = charge × (1 − rate) − fixed

Solve that for the charge:

charge = (net + fixed) ÷ (1 − rate)

Plug in a $100 target at Stripe's rate:

charge = (100 + 0.30) ÷ (1 − 0.029) = 100.30 ÷ 0.971 ≈ 103.30

Charge $103.30 and you net $100 on the dot. Add the fixed fee before dividing because it gets charged no matter what; divide by (1 − rate) because the percentage is taken on the new, larger total. If you ever see the percentage hit 100% or more, no finite charge can net you anything — a good calculator flags that instead of returning nonsense. The payment processing fee calculator runs this gross-up automatically in its reverse mode, so you type the target and read the price.

Comparing Stripe and PayPal on real orders

Fee differences look tiny per order and large per year. Take a $250 sale.

Stripe at 2.9% + $0.30:

fee = 250 × 0.029 + 0.30 = 7.25 + 0.30 = 7.55
net = 242.45

PayPal at 3.49% + $0.49:

fee = 250 × 0.0349 + 0.49 = 8.725 + 0.49 = 9.215 ≈ 9.21
net = 240.79

That is $1.66 per order in Stripe's favor. On 500 orders a month, the difference is about $830 a year — enough to justify steering checkout toward the cheaper rail or negotiating your PayPal rate. The lesson is to compare on your actual ticket size, not on the percentage alone, because the fixed fee shifts the balance differently for small and large charges.

Cross-border charges change the picture again. International cards cost processors more, so they add a surcharge — Stripe adds roughly 1% for international cards and about 1% more on a currency conversion, pushing the effective rate toward 3.9–4.9%. Always confirm against your own fee schedule and edit the percentage to match before you trust the net.

Why splitting fees is tricky

Because the fixed fee is per transaction, how you slice payments matters more than people expect. Split one $100 order into ten $10 charges and you pay the $0.30 fixed fee ten times — $3.00 instead of $0.30 — even though the percentage portion is identical either way:

one $100 charge:   fee = 100 × 0.029 + 0.30  = 3.20
ten $10 charges:   fee = 10 × (10 × 0.029 + 0.30) = 10 × 0.59 = 5.90

The split costs $2.70 more for the exact same money moved. The reverse is just as true for splitting a fee between parties: if two people share a $100 bill and you want each to cover their half of the fee, you cannot simply halve the gross-up, because the fixed $0.30 does not divide neatly and the percentage interacts with whatever each person's share is. Decide who absorbs the fixed fee before you do the math, then gross-up each share separately.

One more subtlety: many jurisdictions and some processor agreements restrict or ban surcharging card payments. Passing the fee to the customer through a higher price is usually fine; adding an explicit "card fee" line may not be. Check your processor's rules and local law before you build fee pass-through into checkout.

Putting it to work

The whole discipline comes down to three habits. Read the effective rate, not the sticker, before pricing anything small. Gross-up with charge = (net + fixed) ÷ (1 − rate) whenever you need a clean number to land. And compare processors on your real average order, where the fixed fee actually bites. Once those are second nature, the payout never surprises you again.

If your pricing also has to account for sales tax, the same gross-up thinking applies — see the VAT calculator for the tax-inclusive version of the same problem, where you back out a rate from a total instead of adding it on.

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Made by Toolora · Updated 2026-06-13