Interior room painting is priced by paintable square footage — the sum of all wall surfaces minus 50% of door and window openings. The formula is straightforward, but getting prep right is where margin is won or lost.
Wall Area Formula
Wall Area = (2 × L + 2 × W) × H − (0.5 × door/window area)
Example
A 12×15 room with 9 ft ceilings and two windows: (2×12 + 2×15) × 9 − (2 × 15) = 486 − 30 = 456 sq ft of wall area
Waste factor: 10% standard; 15% for rooms with extensive trim or multiple colors
Walk the room with a tape. Measure each wall individually — L × H — and sum them. Subtract 50% of door and window openings. Do not rely on floor plan dimensions; walls have varying heights around windows and transitions.
Ceiling = L × W. Price it at a different rate than walls — ceiling painting requires more setup, overhead work, and often a different finish. Never bundle ceiling and wall pricing at the same rate.
Walk the surfaces. Count holes, cracks, water stains, and texture inconsistencies. Assign patch-and-prime hours separately from painting hours. Underestimating prep is the #1 cause of margin loss on paint jobs.
Divide total wall area by your coverage rate (standard latex = 350–400 sq ft/gal). Divide by number of coats. Add 10% for waste and touch-up. Round up to the nearest gallon.
Multiply paintable sq ft by your per-sq-ft rate ($1.50–$3.50 depending on ceiling height, number of colors, and surface condition). Add prep hours at your shop rate. Add trim and ceiling as separate line items.
List each paint product at your cost + 20–30% markup. Never show materials at retail — clients expect a markup and the markup covers your sourcing time and waste.
Measure walls, not floors
A 12×15 room has 180 sq ft of floor but 456+ sq ft of wall surface. Painters who quote by floor area systematically under-price their work. Always measure actual paintable surfaces.
Price trim at per-linear-foot, not per-sq-ft
Trim work (baseboards, casing, crown) is slow and skill-intensive. Price it at $2–$5/LF separately from wall pricing. This protects your margin and gives clients a clear picture of the scope.
Build a room-type rate card
Develop flat rates for Small Bedroom ($350–$500), Master Bedroom ($450–$650), Living Room ($550–$850), and Kitchen ($600–$900). Quoting from a rate card is faster and more consistent than measuring every job from scratch.
A skilled painter applies finish coat at 150–200 sq ft/hour on open flat walls with a roller. Trim, cutting in, and overhead work drops productivity to 50–80 sq ft/hour. Use 100–130 sq ft/hour as your blended rate for a typical room when building estimates.
Yes. Primer is always a separate line — it's a separate product, a separate coat, and additional drying time. Include it when painting over dark colors, new drywall, or water-stained surfaces. Hiding it in the per-sq-ft rate makes the rate look high without explanation.
Taller ceilings add wall area and increase productivity loss from extended-handle work. A 12×15 room at 10 ft has 540 sq ft of wall vs. 486 sq ft at 9 ft — about 11% more area. More importantly, ceilings above 10 ft often require a ladder for cutting-in, which cuts productivity in half. Add a ceiling height surcharge of $0.50–$1.00/sq ft for rooms over 10 ft.
Interior painting labor runs $1.50–$3.50/sq ft of painted surface in 2026, depending on market, surface condition, and detail complexity. New construction (clean surfaces, no furniture) is at the low end. Occupied-home repaints with extensive prep are at the high end. Always price per sq ft of surface — not per sq ft of floor area.
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