Painting Estimate Calculator

This free painting estimate calculator breaks down the full cost of your painting project, from paint gallons to professional labor. Enter your room dimensions below or plug in a known square footage to see exactly what you'll spend on materials, primer, supplies, and optional labor.

1. Choose your input mode. Select "Room dimensions" if you know the length, width, and wall height. Pick "Known square footage" if you've already measured your wall area with a tape measure or laser tool.
2. Enter your room dimensions. For a standard bedroom, you might enter 14 ft × 12 ft × 9 ft. The painting estimate calculator multiplies the perimeter by wall height to get total wall area.
3. Set door and window counts. Each door subtracts 20 sq ft (a standard 6 ft 8 in × 3 ft opening). Each window subtracts 15 sq ft (a typical 3 ft × 5 ft window). These areas don't need paint, so the calculator removes them automatically.
4. Toggle ceiling on if you're painting the ceiling too. The calculator adds length × width to your total paintable area. Ceiling paint often has different coverage, so you may want to adjust the coverage field.
5. Adjust coats, coverage, and paint price to match your project. Most interior projects need 2 coats at 350 sq ft per gallon. Premium paints like Sherwin-Williams Emerald or Benjamin Moore Advance cost $45 to $70 per gallon, while contractor-grade paint runs $20 to $30.
6. Turn on primer if you're painting new drywall, covering stains, or making a dark-to-light color change. The calculator uses 200 sq ft per gallon coverage for primer, which is lower than finish paint because primer is thicker.
7. Enable labor to see what a professional painter would charge. The default $2 per sq ft is typical for simple interior repaints. Adjust up to $4 to $6 for exterior work, high ceilings, or detailed trim work.
8. Click "Calculate painting estimate" to see your cost breakdown.

Pro tip: Get quotes from 3 painters and compare them against this calculator's labor estimate. On my last bedroom repaint, two contractors quoted $450 and $650 for the same 12 × 14 room. Running the numbers here first helped me spot the outlier and negotiate a fair price of $500.

When to use primer

Skip primer on walls that are already painted in a similar color with no stains or damage. Use primer when painting over new drywall, joint compound patches, water stains, smoke damage, or when switching from dark to light colors. A good primer coat saves you from needing a third or fourth coat of expensive finish paint.

Assumptions and limitations

This painting estimate calculator uses standard door (20 sq ft) and window (15 sq ft) deductions. Your actual openings may differ. Measure large picture windows, sliding glass doors, or bay windows separately for a more accurate estimate.

The supply cost estimate ($25 base + $0.02 per sq ft) covers painter's tape, a roller frame, roller covers, a paint tray, and a plastic drop cloth. It does not include ladders, sprayers, or scaffolding. For exterior projects, budget an additional $100 to $300 for scaffolding or extension ladder rental.

Paint coverage varies by surface texture. Smooth drywall covers 350 to 400 sq ft per gallon. Textured walls, stucco, and rough wood siding drop coverage to 200 to 300 sq ft per gallon. Adjust the coverage field to match your surface.

Interior vs exterior painting costs

This painting estimate calculator combines paint quantity math with cost estimation to give you a complete project budget. Every number comes from the formulas below, and you can adjust the paint price, coverage, and labor rate to match your specific project.

Wall area

For room dimensions mode, the calculator finds wall area by doubling the sum of length and width (the perimeter) and multiplying by wall height. A 14 ft × 12 ft room with 9 ft walls has a perimeter of 52 ft and a wall area of 468 sq ft.

Door and window deductions

Each standard door subtracts 20 sq ft (roughly 3 ft × 6 ft 8 in). Each window subtracts 15 sq ft (roughly 3 ft × 5 ft). A room with 1 door and 2 windows loses 50 sq ft of paintable area. Skip these deductions on rooms with no openings or adjust the counts for oversized windows or double doors.

Paint gallons

Multiply total paintable area by number of coats, then divide by coverage per gallon. The calculator rounds up to whole gallons because paint stores don't sell partial gallons. Most latex interior paints cover 350 to 400 sq ft per gallon on smooth drywall.

Primer cost

When primer is enabled, the calculator estimates 1 coat at 200 sq ft per gallon. Primer is thicker than finish paint and covers less area. The primer price defaults to 70% of your finish paint price, which tracks with most brand pricing.

Supplies and labor

The supply estimate starts at $25 (a basic roller kit, tray, and drop cloth) and scales up with project size at $0.02 per sq ft for extra tape, roller covers, and plastic sheeting. Labor cost multiplies your total paintable area by the rate per sq ft.

Worked example: 12 × 14 ft bedroom

Given:

• Room = 12 ft × 14 ft, wall height = 9 ft
• 1 door, 2 windows, no ceiling, 2 coats
• Coverage = 350 sq ft/gal, paint = $35/gal
• Primer enabled, labor at $2.50/sq ft

Calculations:

• Perimeter = 2 × (12 + 14) = 52 ft
• Wall area = 52 × 9 = 468 sq ft
• Deductions = (1 × 20) + (2 × 15) = 50 sq ft
• Paintable area = 468 − 50 = 418 sq ft
• Paint gallons = ceiling(418 × 2 / 350) = ceiling(2.39) = 3 gallons
• Paint cost = 3 × $35 = $105
• Primer gallons = ceiling(418 / 200) = 3 gallons at $25/gal = $75
• Supplies = $25 + (418 × $0.02) = $33
• Labor = 418 × $2.50 = $1,045
• Total = $105 + $75 + $33 + $1,045 = $1,258
• DIY cost (no labor) = $105 + $75 + $33 = $213

Coverage adjustments by surface

Paint coverage changes with surface texture and type. Use 350 to 400 sq ft/gal for smooth drywall, 250 to 300 for lightly textured walls, and 200 to 250 for heavy knockdown texture, stucco, or rough wood siding. Adjust the coverage field in the calculator to get a more accurate gallon count.