Interior Painting Cost Calculator
Enter your room size, coats, and finish choices to estimate paint, primer, and labor. Wall area is calculated from the room perimeter, not the floor area.
Each door deducts 21 sq ft of wall.
Each window deducts 15 sq ft of wall.
Adds one primer coat priced at $32/gal.
Affects labor only: light ×1.0, moderate ×1.3, heavy ×1.7.
Leave 0 to use the $1.10/sq ft default.
Adds ceiling area (length × width) to paint and labor.
Adds 1 gal of paint and a flat $150 labor allowance.
How We Calculated This
- Wall perimeter = 2 × (room length + room width). Floor area (length × width) is NOT used for walls.
- Gross wall area = perimeter × wall height.
- Opening deduction = doors × 21 sq ft + windows × 15 sq ft.
- Paintable wall area = max(0, gross wall area − opening deduction).
- Ceiling area (only if "Paint ceiling" is on) = room length × room width; added to the area painted for both paint quantity and labor.
- Total coated area = (paintable wall area + ceiling area) × coats.
- Paint gallons = ceil(total coated area ÷ coverage) — rounding up builds in a waste allowance; +1 gallon if trim is painted.
- Primer gallons (only if primer needed) = ceil((paintable + ceiling) ÷ coverage) for a single coat.
- Material cost = paint gallons × paint price + primer gallons × $32/gal (fixed educational primer price).
- Labor = (paintable + ceiling) × labor rate × (1 + 0.5 × (coats − 1)) × prep multiplier (light 1.0, moderate 1.3, heavy 1.7). Trim painting adds a flat $150 labor allowance.
- Total = paint + primer + labor + trim labor + contingency.
- Cost per sq ft of wall = total ÷ paintable wall area.
Assumptions
- Paintable wall area is perimeter-based [2 × (length + width) × wall height], NOT floor area.
- Standard openings deduct 21 sq ft per door and 15 sq ft per window.
- All prices and rates are editable planning assumptions.
- Paint quantity includes waste by rounding gallons up.
What's excluded
- Wallpaper removal
- Major drywall repair
- Lead-paint abatement (pre-1978 homes)
- Trim replacement
Sources & Pricing Methodology
- Editable demonstration dataset (Renovation Cost Lab)Default prices are reasonable planning assumptions, not verified national averages. Replace with local quotes.
Full methodology: how we handle prices.
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