How Much Paint Do I Need?
How much paint do I need? Calculate exactly how much paint to buy - for a whole room or just one wall - so you avoid extra trips to the store or leftover gallons. Enter your room dimensions, and this paint calculator subtracts doors and windows and factors in multiple coats to estimate the gallons (or litres) of paint you need.
Reviewed by the SparkCalc editorial team
How We Calculate This
Wall area = perimeter × height. Subtract 20 sq ft per door and 15 sq ft per window. Multiply by number of coats. Divide by coverage rate and round up to nearest gallon.
Sources: U.S. EPA — Lead Renovation, Repair and Painting (RRP) Program · U.S. EPA — Protect Your Family from Sources of Lead
Frequently Asked Questions
How much paint do I need for one wall?
Multiply the wall width by its height to get the area, subtract any doors (about 20 sq ft each) and windows (about 15 sq ft each), then divide by the coverage rate (350-400 sq ft per gallon) and multiply by the number of coats. A single 10 ft × 8 ft wall usually needs well under one gallon for two coats.
How much does a gallon of paint cover?
Standard paint covers about 350-400 sq ft per gallon on smooth surfaces. Textured walls, bare drywall, or porous surfaces require more paint and may only get 250-300 sq ft per gallon.
Do I need primer?
Use primer when painting over dark colors, stains, new drywall, or drastically changing colors. Many modern paints include primer, reducing the need for a separate coat.
How many coats of paint do I need?
Two coats are recommended for best coverage and durability. One coat may suffice when using paint-and-primer and not making a dramatic color change.
Should I buy extra paint?
Yes, buy 10-15% extra for touch-ups and to account for absorption on textured surfaces. Keep leftover paint for future touch-ups.
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You might also find these calculators helpful: Square Footage Calculator, and Home Affordability Calculator.
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