Interior painting runs $2–$6 per square foot of wall area; exterior painting runs $1.50–$4 per square foot of paintable surface. But the real numbers depend on prep time, coat count, ceiling height, and paint grade. This calculator builds the full estimate — surface area, materials, labor, and margin — so you bid accurately every time.
A skilled painter covers 150–200 sq ft per hour on smooth interior walls (cutting in and rolling). Ceilings slow production by 30–40%. Exterior siding with spray: 300–400 sq ft/hr on smooth surfaces; wood lap siding with brushwork cuts this to 100–150 sq ft/hr. Measure paintable area (deduct windows and doors) rather than total wall area for accurate labor estimates.
Premium interior paint (Benjamin Moore, Sherwin-Williams): $50–$80/gallon. Standard builder-grade: $30–$50/gallon. Coverage: 350–400 sq ft per gallon on smooth surfaces; 200–300 sq ft on porous or textured walls. Primer: $25–$45/gallon. Most contractors mark up paint 20–30% over cost. Add brushes, rollers, tape, and drop cloths as a flat material line item per job.
Prep is where painting margin lives or dies. Sanding, filling holes, caulking, and masking often equals 30–50% of total labor hours on a quality repaint job. New construction has less prep; older homes with lead paint, peeling, or water damage can double it. Always quote prep as a visible line item so customers understand what they're paying for.
Wood siding in poor condition needs cleaning, scraping, priming, and two finish coats — budget $3.50–$5/sq ft. Stucco and masonry absorb more paint and require elastomeric primer on cracked surfaces. Fascia, soffits, and trim are slow to paint and should be priced per linear foot rather than square foot. Soft-wash cleaning before exterior paint: add $150–$400 per project.