How to calculate your chemical cost per car
By Doza · November 4, 2026
Chemical cost per car comes down to two numbers for each product: what one mL costs, and how many mL go on each car. Here's how to work it out, and how to check it against reality.
Step 1: Turn your price into a price per mL
Divide what you pay per gallon by 3,785, the number of mL in a US gallon. A drum at $15 per gallon works out to $0.0040 per mL. Keep four decimal places, because rounding to the cent hides the whole difference at this scale.
Step 2: Multiply by the dose
Do this for each chemical on the wash package, then add them up. The prices and doses below are examples only:
| Chemical | Price per gallon | Price per mL | Dose | Cost per car |
|---|---|---|---|---|
| Presoak | $15 | $0.0040 | 30 mL | $0.12 |
| Foam | $20 | $0.0053 | 15 mL | $0.08 |
| Drying agent | $35 | $0.0092 | 10 mL | $0.09 |
| Tire shine | $50 | $0.0132 | 30 mL | $0.40 |
| Total | $0.69 |
Two things stand out in an example like this. A chemical with a small dose can still be the largest cost, and dilution matters: if a chemical is diluted before it's dosed, use the price per mL of the mixture rather than the concentrate.
Step 3: Check it against what you really used
A calculated number assumes each car gets the planned dose. To test that, take a period with a known car count, add up what you bought or used, and divide:
- Measure each drum at the start and end of the month, adding any deliveries.
- Multiply the gallons used by the price per gallon.
- Divide by the cars washed that month.
If the result is well above your calculated figure, something is off: doses set higher than you think, flow that has drifted, a leak, or cars that get more applications than the plan says.
Step 4: Repeat it without the clipboard
The monthly check tells you there's a gap but not when it started, or at which site. That's the reason we built cost tracking into Doza Pumps. Each dose is recorded as it happens and multiplied by the price you entered for that chemical. DozaLink shows use and cost by site, chemical and device.
Its cost per car uses an estimate of washes, based on the busiest pump at each site in each hour, so compare it with your controller's car count from time to time. When a price changes, new doses use the new price, and earlier doses keep the cost they were recorded with.
Want to see it on real screens? Try the live demo, which runs on demo data.