Coving Calculator — Pieces, Adhesive & Mitre Cuts

Measure the room perimeter (2 × length + 2 × width) and divide by the coving piece length (typically 2m or 3m). Add 10% wastage for mitre cuts and off-cuts. For example, a 3.5m × 4m room has a 15m perimeter, requiring 5 pieces of 3m coving, or about 6 pieces with wastage.

Coving adhesive coverage is measured per metre of run, not per piece. A standard 310ml cartridge (e.g. Diall) covers roughly 4–6 linear metres of coving — about one to two 3m lengths — so a rule of thumb is one cartridge per 5m. A 15m room perimeter therefore needs about 3 cartridges. If you prefer powder adhesive, a 5kg bag of British Gypsum Gyproc Cove Adhesive fixes approximately 15 linear metres (about 3m per kilogram). Always keep a spare on hand.

Use a mitre box or coving mitre template for accurate 45-degree cuts. For internal corners, cut the coving with the ceiling edge flat in the mitre box. For external corners, reverse the cut direction. Many plasterers prefer using a coving template (available from Screwfix and B&Q) which makes cutting much easier and more accurate.

For standard UK rooms with 2.4m ceilings, 100-127mm (4-5 inch) coving is the most popular. Larger rooms with higher ceilings suit 150mm+ coving. Most polystyrene and plaster coving comes in 2m or 3m lengths. 3m lengths are better value and create fewer joints but are harder to handle solo.

Yes, exactly. Enter the overall length and overall width of the bounding rectangle: cutting a notch from a corner does not change the perimeter, because the two notch walls take the place of the wall sections they replace, so the coving run is identical to a full rectangle. Do update the corner counts though: a plain L-shaped room has 6 corners, 5 internal and 1 external (the corner that points into the room), instead of the standard 4 internal. A chimney breast is different: it adds run rather than removing it. Add the depth of the breast to your room length measurement (the calculator doubles the length, which covers both return sides), then count 2 extra internal corners and 2 extra external corners for the breast.

The main types in the UK are: plaster coving (traditional, heavy, requires adhesive), polystyrene coving (lightweight, cheap, easy to fit), polyurethane coving (durable, lightweight, good detail), and Duropolymer coving (moisture-resistant, for bathrooms). Gyproc plaster coving is the standard trade choice. For ornate cornice options, see our Cornice and Coving Calculator.