Two numbers on the label, one that matters
The label gives you a container size and a dilution ratio. The receipt gives you a price. None of those is the cost of the product on the car. That number is the price divided by how many ounces the bottle makes once it is mixed.
Cost per RTU ounce = price ÷ RTU ounces.
| Product | Price | Size | Dilution | RTU ounces | Cost per RTU oz |
|---|---|---|---|---|---|
| All purpose cleaner | $24 | 128 oz | 10:1 | 1,408 | 1.7¢ |
| Wheel cleaner | $32 | 128 oz | 4:1 | 640 | 5.0¢ |
| Car shampoo | $28 | 128 oz | 128:1 | 16,512 | 0.17¢ |
| Interior cleaner | $22 | 128 oz | 4:1 | 640 | 3.4¢ |
| Leather conditioner | $28 | 32 oz | neat | 32 | 87.5¢ |
| Polish and compound | $42 | 32 oz | neat | 32 | $1.31 |
| Ceramic sealant | $65 | 1.7 oz | neat | 1.7 | $38.24 |
The shampoo and the leather conditioner cost the same at the register. On the car one is five hundred times the other. The bottle you flinch at buying, the sealant, is expensive per ounce but you use a few tenths of an ounce per panel; it is a line item, not a shelf cost.
Cost per car is ounces used × cost per ounce
Eight ounces of diluted APC is 14 cents. Sixteen ounces of shampoo is three cents. Two ounces of leather conditioner is $1.75. An ounce and a half of compound is $1.97. A standard interior and exterior detail on this shelf is about $4.50 of product, $5 with a 10% waste allowance. The chemical cost calculator does the whole shelf at once.
Why this changes what you argue about
On a four-hour detail, labour at a loaded $28.75 is $118. Chemicals are $5. Switching to a product that is 20% cheaper saves a dollar. Finding a product that saves ten minutes saves five dollars. Once the cost per car is in front of you, product decisions become time decisions, which is where they belonged.
Where product money actually leaks
- Dilution by eye. A 10:1 product poured at 4:1 costs two and a half times as much per ounce, and stronger is often worse: streaks, residue, dulled trim. Use a measuring cup or a dilution sprayer.
- Mixing more than the day needs. Diluted product in an open bucket loses strength. Mix for the day.
- Buying quarts of gallon products. The same product in a quart typically costs 30% to 40% more per ounce.
- Consumables nobody tracks. Towels are cents per use. Pads are dollars per car. Count the pads.
Vehicles per bottle: when to reorder
RTU ounces ÷ ounces per vehicle. A gallon of shampoo does a thousand cars. A quart of leather conditioner does sixteen. At forty cars a month you reorder conditioner every twelve days and shampoo every two years. Order by vehicles per bottle and the shelf stops surprising you.