Paint Calculator — m, m², liters & cost
How to use this calculator
Pick a surface mode — room walls, ceiling, a single wall, or a known area. Enter dimensions in metres, centimetres or millimetres, choose the finish and number of coats, and a standard door (1.89 m²) and window (1.20 m²) are deducted per opening. Net litres are rounded up to whole tins, since paint is sold by the tin.
Paint types — Flat/Matte (12 m²/L), Eggshell (10), Satin (10), Semi-Gloss (10), Gloss (9).
Primer — 1 coat at 10 m²/L for new plaster, dark-to-light colour changes, or stain blocking.
Cost — price per liter of paint and primer, plus optional flat-rate for supplies. Currency selector: €, zł, Kč, kr.
Saved Calculations
| Time | Mode | Area m² | Paint L | Primer L | Coats | Total |
|---|
How to Estimate Paint for a Room (Metric)
For a four-wall room the paintable area is the wall perimeter times ceiling height, less openings. This tool uses manufacturer coverage figures: one litre rolls roughly 10–12 m² per coat on primed plaster, less on porous or textured surfaces. Two coats is the practical default for colour over a similar base; budget three when going dark, covering bold colour, or working with deep accent bases. After fresh plasterboard installed and jointed, prime first so the topcoat covers evenly and the litre count stays accurate.
How to use this calculator
Choose the surface mode, enter the value with the m/cm/mm unit selector, set the finish and coats, and add doors and windows so their area is removed. Set a waste allowance — 3% for smooth plaster, 5% typical, 10% for heavy texture. Open the cost panel for a per-litre estimate with a currency selector; supplies is a flat job rate for rollers, brushes, tape and drop cloths. Prefer feet and gallons? Use the paint calculator in ft and gallons.
Formulas Used
Paintable area = wall perimeter × height − doors − windows.
Paint liters = ceil(paintable area × coats × (1 + waste%) ÷ coverage per liter).
Primer liters = ceil(paintable area × (1 + waste%) ÷ 10).
Paint Coverage by Finish
Flat/Matte: 12 m²/L — best for ceilings and low-traffic areas. Eggshell: 10 m²/L — most popular for living rooms and bedrooms. Satin: 10 m²/L — kitchens, bathrooms, hallways. Semi-Gloss: 10 m²/L — trim, doors, cabinets. Gloss: 9 m²/L — high-moisture areas and accent surfaces.
FAQ
Do I need primer? Yes for bare plaster, dark-to-light changes, or stain blocking — one coat at ~10 m²/L usually suffices. Self-priming paint can replace it on previously painted, sound surfaces in similar colours.
What about the floor and other finishes? Paint covers walls and ceilings only. For the floor see the flooring pack calculator or carpet by m², and for splashbacks and wet areas the tile and grout calculator. Painting masonry? Block and brick are far more porous — size the wall first with the block wall calculator and expect coverage near the low end.
On paint day
Three things estimators forget. Same batch, same tin — buy every litre of one colour at once and box them (decant into a larger pail and stir) so the lap on the last wall matches the first; mid-tin colour shifts are the #1 callback. Sheen and porosity — bare plaster, fresh joint filler and unsealed timber drink the first coat, so spec primer in the takeoff or expect 30–50% more topcoat than the 10–12 m²/L label number. Cost basis (2025 EU) — mid-grade interior emulsion runs €5–12/L, primer €4–8/L, and trade labour adds €6–15/m² for walls or €12–25/m² for trim & doors. EN 13300 classes coverage and scrub resistance — Class 1–2 is correct for kitchens, bathrooms and high-traffic rooms.
