🔨 Construction et bricolage

Calculateur de Couverture de Peinture (Litres / Gallons)

Calculez exactement la peinture nécessaire : surface des murs moins portes et fenêtres, multipliée par les couches et l'apprêt, avec un facteur de couverture selon la texture de surface et le m²/L spécifique à la marque.

Unités

Couches

Texture de la surface

Sous-couche

Inclure le plafond ?

Pièces

Nom	L	l	Hauteur	Portes	Fenêtres

Peinture nécessaire

0 gal

Surface murale — · Sous-couche —

Pièce	Surface murale	Surface nette

Comment fonctionne le calcul

Surface murale par pièce : 2 × (L + l) × hauteur. Ajoutez éventuellement le plafond = L × l.

Soustrayez les ouvertures : 21 sqft par porte, 15 sqft par fenêtre (≈ 1,95 m² et 1,4 m²).

Peinture nécessaire : aire_nette_totale × couches / couverture_par_gal. La couverture dépend de la texture de la surface : lisse 350, légère 300, forte 250 sqft/gal.

Sous-couche : une couche à environ 200 sqft/gal sur toutes les surfaces. Arrondissez toujours au contenant entier supérieur.

Comment fonctionne le calcul

The calculator works room by room. For each row it takes wall area as 2 × (length + width) × height, optionally adds length × width for the ceiling, then subtracts a flat 21 square feet per door and 15 square feet per window to get net paintable area. Totals across all rooms are multiplied by your coat count and divided by the coverage rate, and the answer is rounded up to whole containers, because you cannot buy two-thirds of a tin.

Surface texture is the coverage rate, and it is the biggest single lever: Smooth gives 350 sqft/gal, Light texture 300 and Heavy texture 250, so a heavily textured wall needs 40 percent more paint than a smooth one for the same area. Coats defaults to 2 and accepts 1 to 5. Turning Primer on adds a separate single coat costed at 200 sqft/gal, reported alongside the topcoat figure rather than mixed into it.

The opening deductions are fixed averages, not measurements: every door counts as 21 sqft and every window as 15 sqft regardless of the real size or the unit system you selected. Trim, doors themselves, closets and soffits are not counted. Metric mode computes in square feet and gallons internally and converts at 3.78541, then rounds to whole litres — which will not line up with the 2.5 and 5 litre tins actually sold, so round to real tin sizes yourself.

FAQ

How much paint do I need for a 12 by 12 foot room?

With 8 foot ceilings that is 384 sqft of wall. Deduct one door and one window and you get 348 sqft net; two coats at the smooth 350 sqft/gal rate works out to 1.99 gallons, which the tool rounds up to 2 gallons.

Do I have to subtract windows and doors myself?

No. Each room row has Doors and Windows count fields. Enter how many of each and the tool removes 21 sqft per door and 15 sqft per window automatically. If a room has an oversized picture window, enter it as two windows to approximate the area.

Does the estimate cover the ceiling as well as the walls?

Only if you set Include ceiling to Yes, which adds length × width to every room's area. It is off by default, and it uses the same texture coverage rate as the walls, so adjust the texture setting if your ceiling is a different finish.

How many coats should I plan for a big colour change?

Keep coats at 2 and switch Primer on. Primer is costed separately as one coat at 200 sqft/gal, which is the standard approach for going dark to light, over patched drywall, or onto bare or glossy surfaces where topcoat alone will not sit evenly.

Why did the total jump a whole gallon after a small edit?

Because the result is rounded up to whole containers. Adding a few square feet can push 1.98 gallons to 2.01 and force a third tin. The per-room table below the result shows the underlying gross and net areas so you can see what actually moved.

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Calculateur de Couverture de Peinture (Litres / Gallons)

Comment fonctionne le calcul

FAQ

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