Manufacturer-stated coverage assumes a smooth substrate at the recommended film thickness. Real-world coverage runs 10-20% lower than the can claim due to spray loss, brush stippling, and substrate absorption. Use realistic defaults when estimating.
Common rates: smooth drywall (Level 4-5 finish) 350 ft²/gal; light orange-peel texture 300 ft²/gal; heavy texture or knock-down 250 ft²/gal; popcorn ceiling 200-225 ft²/gal; stucco or concrete block 175-225 ft²/gal; bare wood 250-300 ft²/gal.
Primer coverage is usually 200-250 ft²/gal — denser product, lower coverage than topcoat. For new drywall, drywall primer (PVA) at 250 ft²/gal is the standard pre-coat.