Product Cost Per Wash Calculator
Turn a bottle's price and size into a real cost per wash based on how much concentrate you actually use each time.
Concentrates look expensive sitting on the shelf next to a cheap ready-to-use spray, but because you only use a small dose per wash, the real cost per wash is usually lower. That is the whole point of buying a concentrate.
How it works
Bottle price by itself doesn't tell you much, since a $35 gallon jug and a $6 spray bottle aren't comparable unless you know how much of each you actually use per wash. The calculator divides the bottle size by your dose per wash to find how many washes the bottle covers, rounding down since a partial dose still counts as a wash, then divides the price by that number of washes to get a cost per wash.
Worked example: a 1 gallon (3785 ml) jug of concentrated wash soap costs $35, and you use 30 ml per wash in a bucket. That jug covers 126 washes, which works out to about $0.28 per wash. Compare that to a $6 ready-to-use spray bottle that only covers 10 washes before it runs out, at $0.60 per wash, more than double the concentrate's real cost.
FAQ
Why does this tool ask for the dose per use, not the bottle's directions?
Bottle directions often give a range or a rough scoop measurement, but people rarely measure exactly to the label. Entering the actual amount you use each time, whether that's 30 ml in a five gallon bucket or a specific number of pump squirts, gives a cost figure that matches how you actually wash, not the label's ideal case.
Does this account for the water and other supplies used per wash?
No, it only prices the one product you enter. Water, microfiber towels, and other consumables have their own costs, but soap and other concentrates are usually the biggest swing between products, so this tool focuses on that comparison.
Why do concentrates look more expensive at the shelf?
A gallon of concentrate costs more up front than a small spray bottle, and that sticker price is what most people compare when shopping. Once you account for how little concentrate goes into each wash, the per-wash cost is usually much lower than a ready-to-use product, even though the bottle itself cost more.
For more on getting the most out of your wash soap, see choosing a car wash soap and what to avoid, the two bucket wash method explained, and essential car detailing supplies for beginners.