Paint Coverage Calculator
Have leftover paint cans or planning a project with a fixed paint budget? Our free Paint Coverage Calculator determines the exact wall surface area your paint quantity can cover. By accounting for surface porosity (smooth drywall, bare wood, brick, concrete), number of coats, and roller nap waste, you can immediately verify if you have enough paint to complete your job.
Project Inputs
Enter your measurements to calculate exact materials
Enter measurements above to view calculation results.
Step-by-Step Calculation Example
Scenario: Calculating finished coverage for 2 gallons of premium interior latex paint applied in 2 coats over standard smooth drywall with a 10% roller buffer.
Determine Gross Single-Coat Capacity: 2 gallons × 350 sq ft/gallon = 700 sq ft.
Apply Surface Porosity: 700 sq ft × 1.0 (smooth drywall) = 700 sq ft.
Deduct 10% Waste Buffer: 700 sq ft × (1 - 0.10) = 700 × 0.90 = 630 sq ft usable coverage.
Divide by 2 Coats: 630 sq ft ÷ 2 coats = 315 sq ft of finished room wall area.
Paint Coverage & Surface Capacity Formula
Finished Coverage = [Paint Quantity × (Coverage Rate × Surface Multiplier) × (1 - Waste%)] ÷ Number of Coats Gross single-coat coverage is calculated by multiplying paint volume by the effective coverage rate (base rate modified by surface texture porosity). A safety buffer (default 10%) is subtracted for roller nap absorption and tray residue. Dividing by the target number of coats yields the net finished room surface that can be fully painted.
Formula Variables
Calculation Assumptions
- Premium interior latex paint on smooth primed drywall covers approximately 350 to 400 sq ft per gallon (8.6 to 10 m² per liter).
- Unprimed drywall and bare wood absorb 20% to 25% more paint on the initial coat.
- Highly porous surfaces like brick, masonry, and stucco reduce effective coverage by 35% to 40%.
- A standard 10% waste buffer is factored in for roller nap retention, cutting waste, and edge touch-ups.
Frequently Asked Questions
Common homeowner and DIY questionsPaint Coverage Calculator
How much wall area does 1 gallon of paint cover?
One standard US gallon of interior latex paint covers approximately 350 to 400 square feet with a single coat on primed drywall. For a standard 2-coat application, 1 gallon will cover 175 to 200 square feet of wall area (such as a small bathroom or accent wall).
How much wall area does 1 liter of paint cover?
One liter of interior wall paint covers approximately 9 to 11 square meters (m²) with a single coat on smooth surfaces. Applying two coats will cover approximately 4.5 to 5.5 square meters per liter.
Do I really need 2 coats of paint, or is 1 coat enough?
One coat is only sufficient if you are refreshing an existing wall with the exact same color and sheen. Two coats are strongly recommended for all other scenarios to achieve uniform sheen, true color depth, full hide, and washability.
How does surface texture and porosity affect paint coverage?
Smooth, previously painted walls require the least amount of paint. Rough textures, unprimed drywall, bare wood, and porous masonry absorb significant moisture, reducing coverage by 20% to 40% on the first coat.
How much paint covers a standard 12x12 bedroom?
A 12x12 bedroom with 8-foot ceilings has approximately 384 gross square feet of wall area (roughly 335 sq ft after deducting 1 door and 2 windows). Applying two coats requires approximately 2 gallons of paint.
Does paint primer have the same coverage as topcoat paint?
Drywall primer covers roughly 250 to 300 sq ft per gallon because it is formulated to seal porous paper and joint compound. Applying primer first prevents your more expensive topcoat paint from soaking into the wall.
How long can leftover paint be stored for future use?
Unopened latex paint can last up to 10 years. Leftover paint that is tightly sealed in an airtight container and stored in a cool, dry place (preventing freezing) will typically remain usable for 2 to 5 years.
Related Tools inInterior Projects
Explore connected calculators for your home project
Paint Calculator
Calculate how much paint you need for walls and ceilings based on room dimensions, doors, windows, and coats.
Drywall Calculator
Estimate drywall sheets (4x8, 4x10, 4x12), screws, joint tape, and joint compound (mud) for wall and ceiling projects.
Room Area Calculator
Calculate square footage, square meters, perimeter, and diagonal corner dimensions for rooms and project planning.
Paint Cost Calculator
Estimate total painting project costs including paint gallons, primer, tools, waste buffer, and professional labor rates.
Wall Area Calculator
Calculate paintable wall area by entering room dimensions, wall height, doors, and windows with customizable opening sizes.