Should you charge extra for oat milk? The maths
1 November 2026 · 4 minute read
Oat milk costs a cafe more than dairy, so most charge extra for it. But a flat surcharge can lose money on large drinks, and some customers see it as a tax on their diet. Here's how to work out what oat milk really costs you, and which way of charging suits your cafe.
The prices below are examples. Put in what you pay.
1. The extra cost per drink
Compare the cost per millilitre, then multiply by the milk in each size.
- Whole milk: £1.30 for 2 litres, so 0.065p a millilitre.
- Barista oat milk: £2.10 a litre, so 0.21p a millilitre.
| Drink | Milk | Dairy | Oat | Extra |
|---|---|---|---|---|
| Flat white | 180 ml | 12p | 38p | 26p |
| Regular latte | 240 ml | 16p | 50p | 34p |
| Large latte | 300 ml | 20p | 63p | 43p |
Allow a little more for the oat milk poured away when steaming. Most cafes lose 5 to 10% of their milk this way.
2. Take VAT out of the surcharge
Hot drinks carry 20% VAT, and that includes the oat milk charge. If you're VAT registered, a 40p surcharge leaves you 33p. That covers the 26p extra on a flat white, but it's 10p short on a large latte.
To cover the extra cost on each size, the charge needs to be at least the extra cost plus VAT:
- Flat white: 26p plus VAT is 31p, so charge 35p.
- Regular latte: 34p plus VAT is 41p, so charge 45p.
- Large latte: 43p plus VAT is 52p, so charge 55p.
That keeps the profit in pounds the same as a dairy drink. The GP percentage still dips a little, because the drink costs more to make. Our guide to a good GP for a cafe explains why that's fine.
3. Three ways to charge
- One flat charge. Simple for staff and customers. Set it to cover your largest size, or you lose money on every large oat latte.
- A charge per size. The fairest to the numbers, but one more thing to get right at the till. Square and most tills can set a different price for an option on each size.
- No charge, with a few pence on every milky drink. Some cafes drop the surcharge because customers notice it. Say you sell 400 milky drinks per week and 100 are oat, at about 30p extra each. That's £30 per week, or 7.5p a drink across all 400. With VAT, 10p on every milky drink covers it.
4. Check it with your own sales
The right answer depends on how many oat drinks you sell, and in which sizes. Your till knows: look for the oat milk option in your item or modifier sales report. Then check a few drinks in the free GP calculator.
Quokka does this from your Square sales every night. It costs oat milk and other extras on every drink, shows whether each charge covers its cost, and tells you when an oat milk price rise means it no longer does.