Question 1

How do I calculate coving for a room?

Accepted Answer

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.

Question 2

How much coving adhesive do I need?

Accepted Answer

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.

Question 3

How do I cut coving mitre joints?

Accepted Answer

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.

Question 4

What size coving should I choose?

Accepted Answer

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.

Question 5

Does this calculator work for an L-shaped room?

Accepted Answer

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.

Question 6

What types of coving are available?

Accepted Answer

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. If you are also boarding the room, use our Plasterboard Calculator to estimate sheet quantities.

Coving Calculator — Pieces, Adhesive & Mitre Cuts

How We Calculate This

The formula

Mitre cuts

Standard UK sizes

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