How Much Paint Do I Need?
Gallons needed = (Paintable area × Number of coats) ÷ Coverage per gallon
Most paint covers 350–400 sq ft per gallon on a smooth, primed surface for one coat — textured or unprimed surfaces (stucco, new drywall, masonry) absorb more and can drop coverage to 200–300 sq ft per gallon.
Worked example: A 12×15 ft room with 9 ft ceilings, one door (20 sq ft) and two windows (30 sq ft) deducted, walls only, 2 coats, 350 sq ft/gallon coverage:
- Wall area: perimeter (54 ft) × height (9 ft) = 486 sq ft, minus 50 sq ft openings = 436 sq ft
- Paint needed: 436 × 2 coats = 872 sq ft ÷ 350 = 2.5 gallons, round up to 3 gallons (or one 5-gallon bucket if buying in bulk)
Interior Painting Cost
| Component | Typical cost |
|---|---|
| Paint (mid-grade interior) | $30–$60 per gallon |
| Paint (premium interior) | $50–$90 per gallon |
| Professional labor (walls, per sq ft) | $1.50–$3.50 |
| Professional labor (ceiling, per sq ft) | $1.50–$3.00 (higher for high ceilings/textured surfaces) |
| Full room (average bedroom, DIY material only) | $150–$350 |
| Full room (average bedroom, professionally painted) | $500–$1,200 |
A typical 12×15 ft room professionally painted (walls + ceiling, 2 coats) runs roughly $700–$1,500 depending on region and prep work needed.
Interior vs. Exterior Paint Coverage
Exterior paint generally covers less area per gallon than interior paint on the same nominal surface, because siding, stucco, and masonry textures absorb more paint than smooth interior drywall — budget 250–350 sq ft per gallon for exterior smooth siding, and as low as 150–250 sq ft per gallon for rough stucco or unpainted masonry.
Ceiling Paint — A Separate Calculation
Ceilings are almost always painted in a flat/matte finish (different from wall sheen) and are calculated by floor area, not wall height — a 12×15 ft room has a 180 sq ft ceiling regardless of ceiling height. Don’t reuse your wall paint total for the ceiling; calculate it as its own line item, since it’s frequently a different product entirely (ceiling paint is formulated to resist drips and hide imperfections differently than wall paint).
Major Paint Brands — Coverage Reference
Sherwin-Williams, Behr, and Benjamin Moore are the most-searched paint brands, and all publish their own coverage estimates per product line — typically in the same 350–400 sq ft per gallon range this calculator uses as a default, though premium and specialty lines (elastomeric, high-hide, or deep-base colors) can vary. This calculator is an independent, brand-agnostic estimate — always confirm the exact coverage rate printed on your specific can, since it varies by sheen, base, and color depth even within one brand’s product line.
Frequently Asked Questions
How much paint do I need for a room?
Multiply your total wall (and ceiling, if included) area by the number of coats, then divide by your paint’s coverage rate — typically 350–400 sq ft per gallon. A 12×15 ft room with 9 ft ceilings needs roughly 2.5–3 gallons for two coats on the walls.
How much does it cost to paint a room?
A professionally painted average bedroom (walls and ceiling, two coats) typically costs $700–$1,500 including labor and material. DIY material-only cost for the same room runs roughly $150–$350.
How much does exterior painting cost?
Exterior painting typically costs more per square foot than interior due to prep work, ladders/scaffolding, and lower paint coverage on textured surfaces — expect $2.50–$6.00+ per square foot professionally installed, varying significantly by siding material and home height.
How much paint coverage do I get per gallon?
Most paint covers 350–400 sq ft per gallon on a smooth, primed surface. Textured or unprimed surfaces like stucco, new drywall, or masonry can drop coverage to 200–300 sq ft per gallon, so always check your specific product’s label.
Do I need to paint a ceiling separately from the walls?
Yes — ceilings are calculated by floor area (not wall height) and typically use a different flat/matte-finish product designed to resist drips, so calculate and budget for ceiling paint as its own line item.
How many coats of paint do I need?
Two coats is standard for most interior and exterior jobs, especially over a different existing color or bare drywall/wood. A single coat may suffice for a touch-up in the same color over a well-prepped, similarly colored surface.
How much does it cost to paint a fence?
Fence painting cost depends heavily on fence style (privacy vs. picket) and material — expect roughly $1–$3 per linear foot for a standard picket fence, more for a solid privacy fence with more surface area per foot.
How much does Sherwin-Williams, Behr, or Benjamin Moore paint cost per gallon?
Pricing varies by product line, but mid-grade interior paint from major brands commonly runs $30–$60 per gallon, with premium lines running $50–$90+. This calculator is an independent estimate, not affiliated with any specific brand.
How do I calculate square footage for painting?
Multiply each wall’s length by its height, sum all walls, then subtract door and window openings. For a ceiling, multiply the room’s length by width. The calculator above does this automatically as you enter your room dimensions.
Can I use this instead of my paint retailer’s calculator?
Yes, as an independent, brand-agnostic estimate to sanity-check any retailer’s or manufacturer’s tool. Coverage rates vary by product, sheen, and color depth even within one brand, so always confirm against your specific can’s label before ordering.
Get free quotes from local painting contractors
Prep and sheen change the real gallon count. Get 2–3 painter quotes before you commit to a whole-house job.