Every datasheet quotes coverage in m²/L or m²/set. That number assumes a smooth, sealed, level substrate and no waste. Real substrates are none of those things.
The three deductions
- Substrate porosity. A fresh unsealed screed can take 15–25% more on the first coat than the datasheet says.
- Profile and texture. A shot-blasted slab at CSP 3 has considerably more surface area than its plan area.
- Waste. Roller loading, cut-in, decanting and what stays in the pail. Allow 5–10% on liquids, more on small pack sizes.
The coverage calculator on each product page does this arithmetic against the area and coat count you enter, and rounds up to whole packs. It gives you a quantity you can put on a purchase order, not a theoretical figure.
Add the result to your order and send it. Every order is priced by a person against the quantity and the delivery address, so what you get back is a real number with the freight in it — not a shelf price you then have to argue about.
Written by the INTRIC technical desk. If this raised a question about your substrate, ask it — send the detail and you get an answer, not a sales call.