How Much Paint Do I Need? Room-by-Room Guide (2026)

Buying too much paint wastes money. Buying too little means a trip back to the store mid-project. This guide shows exactly how to calculate how much paint you need per room — with real examples.

The Basic Paint Formula

Wall area = (Room Perimeter × Wall Height) − Doors − Windows

One gallon of paint covers about 350–400 square feet in one coat. Most rooms need 2 coats.

Step-by-Step: How to Calculate Paint Needed

1. Measure the room: length × width
2. Calculate perimeter: 2 × (length + width)
3. Multiply by ceiling height (usually 8 ft)
4. Subtract 20 sq ft per door, 15 sq ft per window
5. Divide by 350 (coverage per gallon)
6. Multiply by number of coats (usually 2)

Example: 12 × 14 ft Bedroom

• Perimeter = 52 ft
• Wall area = 52 × 8 = 416 sq ft
• Minus 1 door (20) + 2 windows (30) = 366 sq ft
• For 2 coats: 366 × 2 = 732 sq ft
• 732 ÷ 350 = ~2.1 gallons

Buy 2 gallons + 1 quart for touch-ups. Or use our paint calculator for instant numbers.

How Much Paint Per Room Type (Quick Reference)

Room	Avg Size	Paint Needed (2 coats)
Small bedroom	10 × 10 ft	1.5 gallons
Master bedroom	14 × 16 ft	2.5 gallons
Living room	16 × 20 ft	3 gallons
Bathroom	5 × 8 ft	1 gallon
Kitchen	10 × 12 ft	2 gallons
Ceiling (per room)	Avg 200 sq ft	1 gallon

What Affects Paint Coverage?

• Texture: Rough walls absorb more paint
• Color change: Dark → light needs 3 coats + primer
• Paint quality: Premium paints cover better (sometimes 1 coat)
• Sheen: Flat covers best; gloss needs more coats

Do I Need Primer?

Yes, if:

• Painting over dark colors
• Painting over new drywall
• Painting over stains or repairs
• Switching from oil to latex paint

Frequently Asked Questions

How much paint do I need for a 12x12 room?

About 2 gallons for 2 coats, assuming 8-foot ceilings and standard doors/windows.

How many square feet does 1 gallon of paint cover?

350–400 sq ft per coat on smooth interior walls.

Do I need 1 or 2 coats of paint?

Always 2 coats for even coverage and durability — unless using paint-and-primer-in-one over a similar color.

How much does 1 gallon of paint cost?

$25–$70 depending on brand and quality. Premium paints often need fewer coats.