How much plaster or render do I need?
Skimming a wall or rendering one — enter the area, pick the product and get the number of 25 kg bags to buy, allowing for the number of coats and a bit of wastage for what sets in the bucket. Coverage varies a lot by product, so check it against your bag. Free, no sign-up.
A guide, not a guarantee. Plaster and render coverage varies a lot by product, thickness and how flat the wall is, so the figure above is a typical default you should check against your own bag. We size by area × coats ÷ coverage, plus wastage for what sets in the bucket. Site-mixed sand-and-cement render is better worked out by volume — use our patio or concrete tools for the mix. Bonding agent, beads, scrim tape and PVA are extra. Nothing you type leaves your browser.
Area, coats, and coverage per bag.
Start with the area. Length times height gives the wall area; add the ceiling or another wall with the extra-area box, and take off doors and windows you won't be plastering.
Multiply by the coats. Skim is usually two thin coats; a bonding or hardwall undercoat is one thicker coat. We multiply the net area by the number of coats to get the total surface to cover.
Divide by the coverage. Every product has a different coverage per 25 kg bag, depending on how thick it goes on. We set a typical figure when you pick the product — but coverage genuinely varies, so always check the figure printed on your bag and adjust it here.
Add a little wastage. Plaster goes off in the bucket and some is always lost in mixing and on the hawk, so we add about 10%. Mix only what you can apply before it sets.
What this leaves out. A bonding agent or PVA, metal beads and stop-ends, scrim tape for joints, and a backing coat under skim on bare blockwork. Site-mixed sand-and-cement render is worked out by volume instead — use our patio or concrete tools for that mix.
Keep every room's jobs in one place.
Stead remembers your rooms, their sizes and the finishes you chose — so the next decorating job starts with the numbers already to hand.