How to Calculate How Much Paint, Wallpaper, or Flooring You Need for Any Room

Nothing’s more frustrating than running out of paint halfway through a room or ordering too much flooring and wasting money. Before you start your next home improvement project, use our Geometry Calculator to calculate exact material quantities. All you need are your room’s dimensions and a few simple formulas.

How to Calculate Paint Needed for a Room

Paint coverage is typically 350–400 square feet per gallon for a single coat. Here’s how to figure out exactly how much you need:

1. Measure the room perimeter — Add the length of all walls. For a 12′ × 14′ room: 12 + 14 + 12 + 14 = 52 linear feet.
2. Multiply by ceiling height — 52 ft × 8 ft ceiling = 416 sq ft of wall area.
3. Subtract windows and doors — Average door: 21 sq ft. Average window: 15 sq ft. Subtract about 36–51 sq ft for a typical room.
4. Divide by coverage per gallon — (380 sq ft after subtraction) ÷ 350 sq ft/gallon = ~1.1 gallons. So buy 2 gallons for two coats.

Quick Reference: Paint Quantities by Room Size

Room Size	Wall Area	Paint (1 coat)	Paint (2 coats)
10′ × 10′ bedroom	320 sq ft	1 gallon	2 gallons
12′ × 14′ bedroom	416 sq ft	1–2 gallons	2–3 gallons
12′ × 16′ living room	448 sq ft	1–2 gallons	2–3 gallons
14′ × 18′ master bed	512 sq ft	2 gallons	3 gallons
20′ × 20′ great room	640 sq ft	2 gallons	4 gallons

Flooring Calculations

Flooring is sold by the square foot. Measure your room’s length and width, multiply them to get the area, and add 10% for waste and cuts:

Flooring Type	Room Size	Area	+10% Waste	To Order
Hardwood/LVP	12′ × 14′	168 sq ft	17 sq ft	185 sq ft
Carpet	12′ × 14′	168 sq ft	17 sq ft	185 sq ft
Tile (diagonal pattern)	10′ × 12′	120 sq ft	18 sq ft (15%)	138 sq ft

Wallpaper: Calculate Rolls Needed

A standard wallpaper roll covers about 57 square feet (30′ × 21′ roll). Calculate wall area, divide by 57, and round up. For pattern matching, add an extra 15–20%.

• 10′ × 10′ room with 8′ ceilings: 320 sq ft wall area ÷ 57 = 6 rolls
• 12′ × 14′ room with 8′ ceilings: 416 sq ft ÷ 57 = 8 rolls
• Add 1–2 extra rolls for pattern matching, waste, and future repairs

For any room shape — rectangle, L-shaped, or irregular — our Geometry Calculator handles area, perimeter, and volume calculations instantly. Enter your measurements and get exact results for paint, flooring, wallpaper, concrete, tile, and more.