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Paint Calculator - How Much Paint Do I Need?

Enter your room size and coats. Get the gallons of paint to buy.

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Units
Room size (ft)

Quick fill:

How do I measure this?
  1. Run a tape measure along one wall at floor level - that's the length.
  2. Measure the wall at a right angle to it - that's the width. For an L-shaped room, split it into rectangles and add them up.
  3. Write both numbers down before you shop - a phone photo of the tape works great.

Presets are rough starters - measure your real room before ordering.

Advanced

Paint to buy

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Enter your room dimensions to see how much to buy.

See what painting this room costs →

💡 Buy about 10% extra - custom colors are hard to match later.

⚠️ Prime bare or patched spots - unprimed areas dry blotchy.

Paint roller and a fresh paint stroke - paint quantity calculator

How to estimate paint

  1. Measure the room's length, width and wall height.
  2. Wall area = 2 × (length + width) × height, less ~15% for doors and windows.
  3. Multiply by coats, then divide by coverage and round up to whole units.

Paint coverage, and what changes it

One gallon of interior paint covers roughly 350–400 ft² per coat (about 9–11 m² per litre) on a smooth, primed wall. Real coverage drops on textured, porous or unprimed surfaces and with deep colors, so it's smart to buy a little extra and keep some for touch-ups. Primer covers less - about 200–300 ft² per gallon - so estimate it separately.

Frequently asked questions

How much paint do I need for a 12×12 room?
A 12×12 ft room with 9 ft walls has about 340 ft² of wall (after doors and windows). Two coats need roughly 680 ft² of coverage, or about 2 gallons at 350 ft²/gallon. Enter your exact dimensions above.
How much does a gallon (or litre) of paint cover?
About 350–400 ft² per gallon per coat (≈9–11 m² per litre) on a smooth, primed wall. Textured, porous or unprimed surfaces soak up more, so real coverage can be lower - the number is on the can.
One coat or two?
Most jobs need two coats for even color and durability, especially over a different color. A same-color refresh on a clean wall can sometimes get by with one.
Do I need primer too?
Prime new drywall, patches, stains or big color changes. Primer covers less - about 200–300 ft² per gallon - so estimate it separately from your finish paint.

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