Gloss Paint Calculator — Doors, Frames & Skirting

A standard UK internal door leaf is 1981mm × 762mm = 1.51 m² per face, so glossing both faces is about 3.0 m² (Dulux puts a door at roughly 2 m² per coat per side, ≈4 m² for both sides once you include edges). At 16 m²/L coverage for gloss, one door needs about 0.19 L per coat, or 0.38 L for two coats. A 750ml tin therefore covers roughly 2 doors with two coats. Don't forget the door frame — each linear metre of frame adds about 0.5 m² (rule of thumb, both faces of the lining plus architrave).

Yes, undercoat is strongly recommended before gloss paint. Undercoat provides better adhesion, builds opacity (especially when changing colours), and gives the gloss topcoat a smooth, even base. On bare wood, use a primer first, then undercoat, then gloss. On previously glossed surfaces in good condition, a light sand and two coats of gloss may suffice.

This calculator uses practical working rates of about 16 m²/L for gloss and satinwood and 14 m²/L for eggshell on smooth prepared surfaces. Manufacturer 'up to' maxima are higher — Dulux Trade High Gloss quotes up to 18 m²/L, Satinwood and Eggshell up to 17 m²/L, and Johnstone's Trade gloss around 17 m²/L — so these working figures err slightly toward ordering more paint, which is safer. Bare or absorbent wood will use significantly more. Water-based gloss may cover marginally less than solvent-based.

Two coats of gloss over undercoat is the professional standard. One coat of gloss rarely gives full coverage or a good sheen. When using water-based gloss, two coats are essential as the first coat can look patchy. Apply thin, even coats — thick coats cause drips and take longer to dry.

Water-based (acrylic) gloss is now the standard in the UK due to VOC regulations. It dries faster (1-2 hours vs 16 hours), has less odour, and yellows less over time. Oil-based gloss gives a harder, shinier finish but takes longer to dry and yellows. For the highest sheen on doors, oil-based is still preferred by many decorators.