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Paint Calculator

Calculate how much paint you need for walls and ceilings — with door and window exclusions, number of coats, and coverage rate

Check the paint can (typically 10–14)

Walls area 45.00 m²
Ceiling area 0.00 m²
Doors + Windows excluded −4.70 m²
Paintable area 40.30 m²

You need

8.06 L

40.30 m² ÷ 10 m²/L × 2 coats

About This Tool

Buying the right amount of paint saves money and trips to the store. Too little means an extra run mid-project with a partially painted room. Too much means wasted paint drying in the garage. This calculator takes your room dimensions, lets you choose walls and ceiling separately, subtracts doors and windows, and factors in the number of coats. Enter your paint's coverage rate (printed on every can) and get the exact number of liters or gallons you need. The math is simple — total paintable area divided by coverage per liter, multiplied by the number of coats — but doing it by hand for a room with three windows and two doors gets tedious fast. This tool does it instantly.

How to Use

1. Enter room dimensions: length, width, and wall height 2. Toggle walls and ceiling — choose what you're painting 3. Set the number of doors and windows to exclude from the calculation 4. Choose the number of coats (most rooms need 2) 5. Enter your paint's coverage rate (check the can — typically 10–12 m²/L) 6. Read the result: total area, paintable area after exclusions, and liters needed

Formula

Walls area = 2 × (length + width) × height Ceiling area = length × width Exclusions = (doors × door area) + (windows × window area) Paintable area = (walls + ceiling) − exclusions Paint needed = (paintable area ÷ coverage per liter) × number of coats

Frequently Asked Questions

How much paint do I need for a 12×12 room?
A 12×12 foot room (3.66×3.66 m) with 8-foot (2.44 m) ceilings has about 384 sq ft (35.7 m²) of wall area. Subtract a door and a window (~25 sq ft / 2.3 m²) and you need roughly 33.4 m² painted. At 10 m²/L with 2 coats, that's about 6.7 liters (1.8 gallons).
How many square meters does 1 liter of paint cover?
Most interior wall paints cover 10–14 m² per liter (400–560 sq ft per gallon) on smooth surfaces. Coverage varies by paint type, surface texture, and color. Dark colors over light walls may need an extra coat. Always check the coverage rate on the paint can.
Do I need 2 coats of paint?
In most cases, yes. Two coats ensure even coverage, true color, and better durability. You may get away with one coat if you're repainting the same color. New drywall, dark-to-light color changes, and bright/deep colors almost always need two coats — sometimes three.
Should I subtract doors and windows when calculating paint?
Yes. A standard door is about 1.9 m² (21 sq ft) and a standard window about 1.4 m² (15 sq ft). For a room with 2 doors and 3 windows, that's 8 m² you don't need to paint. Skipping this means buying 15–20% more paint than needed.
How much paint do I need for the ceiling?
Ceiling area is simply length × width. A 4×5 meter room has a 20 m² ceiling. At 10 m²/L with 2 coats, you need 4 liters of ceiling paint. Ceiling paint is usually thicker with higher coverage — check the can.
What is the difference between wall paint and ceiling paint?
Ceiling paint is formulated to be thicker (less dripping), has a flat/matte finish (hides imperfections), and is usually white. Wall paint comes in various sheens (matte, eggshell, satin, semi-gloss) and colors. You can use wall paint on ceilings, but ceiling paint is easier to apply overhead.

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