Advanced options
The 10% covers the mitres: every internal corner eats coving in matched 45-degree cuts, and the first pair always goes wrong. A paper mitre template or cheap mitre box (sized for your coving profile) turns corners from guesswork into tracing. Adhesive coverage: roughly one tube or 3-4 linear metres per mix: support long runs with a couple of nails under the bottom edge while it grabs.
What The Coving Calculator Works Out
- Perimeter: two lengths plus two widths of the room, the run of wall-ceiling junction the coving has to cover. The standard 4m x 3m room is a 14m perimeter.
- Coving to buy: the perimeter plus 10% for the mitres, divided into 2m or 3m lengths and rounded up. Every internal corner eats coving in matched 45-degree pairs and tradition requires the first pair to be cut wrong, so the 4m x 3m room is eight 2m lengths.
- Adhesive: one tube of coving adhesive per 3.5m of run, applied to both edges, with the squeeze-out wiped as the instant caulk it is. Nails or pins under the bottom edge support long lengths while the grab develops.
- Wastage and extra wall run (advanced): set your own allowance (confident fitters manage 5%, first-timers should keep 10% to 15%) and add the extra metres a chimney breast, alcoves or a bay window put into the run.
- Internal and external corners (advanced): a plain room has four internal corners; a chimney breast adds two external and two internal. Each corner is two matched mitre cuts, and the card counts them along with the tubes of filler or caulk for the joints.
- Coving profile and pencil guide lines (advanced): the 127mm "C" profile is the British default, 90mm to 100mm the modern low-ceiling kindness, 150mm for high ceilings. The guide-line card gives the wall drop and ceiling projection (the face width divided by root 2, so 90mm for 127mm coving) to pencil round the room so the run stays straight where the ceiling is not.
- Coving cost (advanced): lengths x your price, with a cost per metre of wall. Paper-faced gypsum coving is typically GBP 4 to GBP 8 a 2m length and paints like plaster; polystyrene is GBP 2 to GBP 4 but dents and shows its joints.
- Adhesive coverage and rooms (advanced): edit the metres per tube from your adhesive's own label (powder mixes stretch further) and multiply everything for several identical rooms.
- Wall-by-wall count (advanced): an alternative count that gives each wall whole lengths with no sharing of offcuts, with a table of full lengths and the last cut piece per wall. Buy this number if you would rather not join offcuts above doors; coving's real job is hiding the cracks, waves and settlement lines of the wall-ceiling junction behind a clean curve.