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Paint Coverage Estimator - Online Wall Area & Cans Needed

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Paint Coverage Estimator

Calculate wall area & paint cans needed for your room

QUICK FILL:
Room Dimensions
ft
ft
ft

Doors & Windows
sq ft
Standard: ~20 sq ft
Doors total: 40 sq ft
sq ft
Standard: ~12 sq ft
Windows total: 24 sq ft
sq ft
Deduction area exceeds total paintable surface. Please check your inputs.

Paint Settings
coats
2 coats recommended for new walls
sq ft/gal
Typical: 350-400 sq ft/gal
gallon(s)
Standard can: 1 gallon
Imperial Β· sq ft / gallons
2

Cans Needed (minimum)

Recommended purchase: 3 cans (+10% buffer)


Total Wall Area
384 sq ft
Ceiling Area
β€”
Deductions
-64 sq ft
Net Paintable Area
320 sq ft
With Coats (Γ—2)
640 sq ft
Exact Cans Required
1.83 cans
Coverage used per can 91%

Frequently Asked Questions

How do I calculate wall area for painting?
To calculate wall area, measure the perimeter of your room (2 Γ— length + 2 Γ— width) and multiply by the ceiling height. This gives you the total wall surface area. Then subtract the area of doors, windows, and other openings. A standard door is about 20 sq ft (1.86 sq m), and a standard window is about 12 sq ft (1.11 sq m). Our calculator does all of this automatically.
How much area does one gallon of paint cover?
On average, one gallon (3.785 liters) of paint covers approximately 350 to 400 square feet (32 to 37 square meters) per coat on smooth, primed surfaces. Coverage varies based on surface texture, porosity, paint quality, and application method. Rougher surfaces like stucco or unpainted drywall may reduce coverage to 250-300 sq ft per gallon. Always check the manufacturer's label for specific coverage information.
How many coats of paint do I need?
Most painting projects require at least two coats for even, durable coverage. If you're painting over a similar color with high-quality paint, one coat may suffice. Painting over dark colors with lighter ones, or painting new drywall, typically requires 2-3 coats. Using a primer can reduce the number of finish coats needed and improve adhesion.
Should I buy extra paint beyond the calculated amount?
Yes! We recommend purchasing 10-15% more paint than the exact calculation suggests. This accounts for touch-ups, spills, absorption variations, and ensures you have matching paint from the same batch. Having extra paint is especially important for future touch-ups, as color matching between different batches can vary slightly. Our calculator includes a recommended purchase amount with a 10% buffer.
Do I need to include the ceiling in my calculation?
Only if you plan to paint the ceiling. Ceiling area is simply length Γ— width of the room. If you're painting the ceiling the same color as the walls, check the "Include ceiling area" option. If using a different color or finish, calculate the ceiling separately. Ceilings often require different paint (flat/matte finish) than walls, so factor that into your planning.
What affects paint coverage the most?
Key factors include: surface texture (rough surfaces absorb more paint), porosity of the substrate (new drywall is very absorbent), paint quality (higher-quality paints have better hide and coverage), application method (rollers vs. sprayers), color change (dramatic color changes may need extra coats), and whether a primer was used. Temperature and humidity during application can also affect coverage and drying.
How do I convert between imperial and metric paint measurements?
1 US gallon equals approximately 3.785 liters. 1 square foot equals 0.0929 square meters. A typical coverage of 350 sq ft per gallon translates to roughly 8.5-9 square meters per liter. Our calculator handles both imperial (feet, gallons, square feet) and metric (meters, liters, square meters) units. Simply toggle between the two systems using the switch at the top.
What are standard door and window sizes for area deduction?
A standard interior door is approximately 80 inches tall by 36 inches wide (203 Γ— 91 cm), which equals about 20 square feet (1.86 sq m). Standard windows vary, but a common size is 48 Γ— 36 inches (122 Γ— 91 cm), about 12 square feet (1.11 sq m). For larger sliding doors or bay windows, measure the actual dimensions. Our calculator uses these defaults but allows you to customize the area per opening.