How Much Paint Do I Need?

The Quick Answer

For an average 12' x 14' room with 8' ceilings, you need approximately 2 gallons of paint for two coats. But let’s break down exactly how to calculate this for any room.

Step 1: Measure Your Walls

Measure the length of each wall and multiply by the ceiling height. For a rectangular room, the formula is:

Total Wall Area = 2 × (Length + Width) × Height

For our example room: 2 × (12 + 14) × 8 = 416 sq ft

Step 2: Subtract Doors and Windows

Standard doors are about 21 sq ft (3' × 7') and standard windows are about 15 sq ft (3' × 5'). Subtract these from your total:

416 - 21 (door) - 30 (2 windows) = 365 sq ft of paintable area

Step 3: Calculate Gallons

One gallon of paint covers approximately 350 sq ft. For two coats:

365 × 2 ÷ 350 = 2.09 gallons

Add 10% for waste and touch-ups: ~2.3 gallons, so buy 3 gallons (or 2 gallons + 2 quarts).

Tips for Accurate Estimates

• Textured walls absorb more paint — plan for 300 sq ft per gallon instead of 350.
• Dark-to-light color changes may need 3 coats. Use a tinted primer first.
• Buy a little extra for future touch-ups. Paint stores can store your color formula.

Use Our Free Calculator

Skip the math — our Paint Calculator handles all of this instantly. Just enter your room dimensions and get an accurate gallon estimate with cost.