Paint Calculator by Square Feet: Coverage, Coats, and Cost

Professional painters estimate by square footage because it is the most reliable method. This guide explains how to calculate paint needs from square footage, what coverage rates to use, and how to adjust for real-world conditions.

Standard Coverage Rates

Surface Type	Sq Ft per Gallon (1 coat)
Smooth interior walls	350-400
Textured walls	250-300
Fresh drywall (primed)	350-400
Fresh drywall (unprimed)	200-250
Ceiling (smooth)	400-450
Ceiling (textured)	300-350
Trim and doors	300-400

The Calculation

1. Measure total square footage to paint.
2. Divide by coverage rate for your surface.
3. Multiply by number of coats.
4. Round up to the nearest quart or gallon.

Example: 500 sq ft of smooth walls, two coats.

• 500 / 375 = 1.33 gallons per coat
• 1.33 x 2 = 2.66 gallons
• Round up: 3 gallons

Coat Adjustments

• Same color refresh: One coat often sufficient.
• Light over dark: Two coats minimum.
• Dark over light: Two coats, possibly three for deep reds or blues.
• Primer + paint: One coat primer, one coat paint on previously painted surfaces.

Buying Strategy

Always round up. It is better to have a quart left over than to run out mid-wall. Paint stores can tint quarts to match if you need more later, but slight batch variations exist.

Using Our Calculator

Our paint calculator does the math automatically. Input your room dimensions, surface type, and number of coats. It tells you gallons needed and estimated cost.

Cost Per Square Foot

• Economy paint: $0.08-0.12 per sq ft per coat
• Mid-grade paint: $0.12-0.18 per sq ft per coat
• Premium paint: $0.18-0.30 per sq ft per coat

For a 12x12 room with two coats using mid-grade paint:

• 384 sq ft walls x 2 coats = 768 sq ft
• At $0.15/sq ft: $115 in paint

Use our calculator to budget your next painting project accurately.