Colour cost per gram: the number most salons don't know

Ask a salon owner what a cut costs them and they will tell you to the minute: the stylist’s time, the chair, the wash. Ask what a head of colour costs them and the answer changes shape. It becomes a shrug, a rough tube count, or a number from the wholesaler’s invoice divided by however many colour clients came through that month.

That is not a criticism. It is a measurement problem. Time is easy to see — it is in the diary. Colour disappears into a bowl.

Why the tube is the wrong unit

A tube of colour is a purchasing unit. It is not a serving unit.

When you price by the tube, you are making an assumption that every head uses a neat fraction of one — a half, a third, a whole. Real heads do not work like that. A short root touch-up and a long balayage might both be logged as “a colour,” and the second one might use four times the product of the first. Priced by the tube, they look identical on paper.

The gap between those two heads is where the money is. And it stays invisible for as long as the unit of measurement is the tube.

What weighing actually shows

Put a scale under the bowl and the picture changes immediately. You stop seeing “a colour” and start seeing 46 grams of one shade, 18 of another, 64 of developer. Multiply each by its cost per gram and you have the true product cost of that head — not an average, not an allocation, the actual number.

Across 19,949 colour bowls weighed inside our own salons, three things came up again and again:

• Overmixing is the default. When you cannot see the cost, the safe move is always to mix a bit more. Nobody wants to run out halfway through a head with foils in. So everyone rounds up, every time, and the rounding never gets measured.
• The same service costs wildly different amounts. Two stylists doing the same service on the same hair length routinely mixed different quantities. Neither was wrong. Nobody had ever shown them the number.
• The waste is not in the expensive shades. It tends to be in the everyday ones — the shades used constantly, where a few extra grams per head compounds quietly across hundreds of heads a month.

You cannot charge a client for the colour that went down the plughole. You can only stop mixing it.

How much does a head of colour cost? A worked example

Here is the sum with example figures. Swap in your own prices from your wholesaler invoice; nothing below is a number you have to take on trust.

Step 1: turn each product into a cost per gram. Divide what you paid by the grams (or millilitres) in the pack. A 60 g tube bought at £8.40 is 14p a gram. A 1 litre bottle of developer bought at £9 is 0.9p a gram.

Step 2: cost the bowl. Say the stylist mixes 40 g of one shade, 20 g of another and 60 g of developer.

Step 3: compare it with the price. On a £95 colour service, £8.94 is 9.4% of the price.

Step 4: price the leftovers. If 15 g of that 120 g bowl is still in the bowl at the end, that is an eighth of the mix, about £1.12 rinsed away on this one head. At 60 colour heads a week, the same habit comes to roughly £67 a week, or about £3,500 a year. Your leftover figure is the one to measure, not to guess.

If you only have invoices and no scale yet, you can still get an average. Monthly colour and developer spend times twelve, divided by colour heads a week times fifty-two, is your cost per head: £2,400 a month across 60 heads a week works out at £9.23 a head. The colour cost calculator does that sum in your browser. Just remember it is an average, and the average is what hides a root touch-up and a full balayage inside the same figure.

The number to actually chase

Once you can see cost per head, the useful number is colour cost as a percentage of the colour service price.

That last row matters more than it sounds. The point of measuring per stylist is not to police anyone. It is that a stylist who consistently overmixes has never been shown what a correctly sized bowl looks like for that service. That is a five-minute conversation, and it only becomes possible once there is a number to talk about.

What changes on the floor

The honest version: not much, and that is the point.

The stylist mixes as they always did. The bowl sits on a scale. The weights land on the client’s record on their own. Nobody stops to write anything down, because anything that requires stopping on a Saturday does not survive contact with a Saturday.

In Daviana ColorLab that scale is an Acaia precision scale connected over Bluetooth. It guides each pour to the gram, shows the product cost of the bowl the moment it is weighed, and takes what was poured off the stock count. If you are comparing the tools that do this, we set out the options, including where the others suit a salon better, in the best hair colour management software for UK salons.

What changes is what you can see afterwards — per head, per stylist, per shade, per month. And what changes after that is what you do about it: the prices that were wrong, the services that were never profitable, the shade that everybody over-pours.

Where the record goes

There is a second benefit that has nothing to do with cost, and salon owners tend to notice it faster than the money.

Because the weights are recorded against the client, the next stylist to colour that client’s hair can see what was actually used last time. Not the formula somebody meant to use, and not a note on a card that may or may not have been updated — the real mix, from the real bowl.

That is the difference between a client whose colour is consistent and a client who quietly stops coming after a visit that did not match the last one. It is also what happens to your colour records when a stylist leaves: if the formula only ever lived in their head or their notebook, it leaves with them.

Start with one week

You do not need a project to find your number. Weigh every bowl for one week and you will have enough to see the shape of it — where the spend actually goes, which services are underpriced, and how big the gap is between mixed and used.

Most owners are surprised by the size of that gap. Almost nobody is surprised by where it is, once they can see it.

If you want to know where to look first, we have written up where colour waste actually happens in a working salon.

Questions salon owners ask