How many square metres does a bag of gypsum cover?
Our undercoat benchmark is one 33 kg bag per 1.3 m² at 2 cm. Enter the actual wall and ceiling area, thickness and bag weight. Confirm the final quantity with your plasterer, allowing for surface unevenness and application.
Coverage and bag-count formula
Measure the walls and ceilings to receive undercoat. Bags = area ÷ 1.3 × thickness in cm ÷ 2 × 33 ÷ bag weight. Round the result up to whole bags.
For example, 13 m² at an average 2 cm requires an estimated 330 kg: ten 33 kg bags. Doubling thickness doubles the estimate. Additional site waste is not included.
A preliminary estimate for a 150 m² unit
Sales’ experience-based example is around 150 bags of 33 kg undercoat plaster for a unit with 150 m² useful floor area: 4,950 kg, approximately 5 tonnes. This is a preliminary purchasing example. Structure, walls, ceilings and the plasterer’s method change the actual amount; confirm each unit’s requirement with its plasterer.
Useful floor area is not plastered surface area. The unit example is not a product consumption rate per square metre of wall or a per-bag coverage figure. For walls and ceilings, use thickness and actual measured consumption.
How do I measure area and thickness?
Multiply each wall length by its height and add the ceilings being plastered. Ask your plasterer to check thickness at several points. A trial area helps estimate consumption on very uneven walls.
What changes between 30, 33 and 40 kg bags?
At an equal consumption rate, a heavier bag covers more area. Bag weight alone does not establish higher quality, whiteness or strength. Compare price per kilogram along with transport and handling requirements.
Calculate bags for your project
Enter the wall and ceiling area to be plastered, average undercoat thickness and bag size. Your estimate updates immediately.
Sales benchmark: one 33 kg bag for 1.3 m² at 2 cm. Thickness and bag size scale proportionally.
Enter a positive area and thickness and select a bag size.
This is an undercoat estimate, rounded up to whole bags with no additional waste allowance. Surface unevenness and application affect consumption; confirm with your plasterer. Plastering area differs from floor area.
Choose a product and view prices →Minimum order is 11 tonnes, handed over at the factory gate. Online payment covers goods only. The driver quotes freight, which you pay directly to the driver. If you have no vehicle, ask sales to help coordinate one.
Your questions, answered
How far does a bag of gypsum-soil plaster go?
Our undercoat benchmark is one 33 kg bag per 1.3 m² at 2 cm. Enter the actual wall and ceiling area, thickness and bag weight. Confirm the final quantity with your plasterer, allowing for surface unevenness and application.
How many bags do I need for 100 m²?
At an average 2 cm, 100 m² of surface needs about 2,538.5 kg, rounded up to 77 bags of 33 kg. This is wall/ceiling area, not floor area; confirm uneven surfaces with your plasterer.