How the calculation works
The formulas
Use net wall area after openings. Enter mixed-volume yield per bag, or convert a coverage specification to volume using its reference thickness. The estimate assumes yield scales linearly with thickness.
Volume = net area × applied thickness
Yield volume = bag yield OR coverage × reference thickness
Bags = ceil(volume × (1 + waste/100) ÷ yield volume)
Assumptions to check
- Use the actual product datasheet. Density, dry bag mass, and mixed yield are not interchangeable.
- Uneven backgrounds and application losses must be reflected in your thickness and allowance.
A worked example
30 m² at 12 mm is 0.36 m³. With 10% waste and 12 L mixed yield per bag, the estimate is 33 bags.