How Do I Calculate How Much Paint I Need?
Multiply room perimeter by wall height to get gross wall area, subtract 21 sq ft per door and 12 sq ft per window, add the ceiling area if you're painting it, multiply by the number of coats, and divide by paint coverage (typically 350 sq ft per gallon). A standard 12×12 room with 8-ft ceilings, ceiling included, one door, and one window needs about 2.83 gallons for two coats of latex.
Paint estimation is the same area math used for drywall and flooring, with one extra wrinkle: paint applies to a surface one or more times depending on color, finish, and substrate. A first coat over fresh drywall covers less than a second coat over a tinted basecoat. The calculator handles this with a coats multiplier.
Gallon formula:Gallons = (wall area + ceiling area) × coats ÷ coverage per gallon. Standard interior latex coverage is 350 sq ft/gal on a smooth primed wall.
How Much Paint for a 12×12 Room?
A 12×12 room with 8-ft walls, 1 door, and 1 window needs 2.83 gallons for two coats of standard latex with the ceiling included, or 2.01 gallons for walls only. The room has 351 sq ft of paintable wall area plus 144 sq ft of ceiling = 495 sq ft total. Round up to 3 gallons (or 2 gallons + 1 quart) for a comfortable cushion.
How Much Area Does a Gallon of Paint Cover?
Standard interior latex covers 300–400 sq ft per gallon for a single coat on a smooth, primed surface. Premium re-coat paints can reach 400 sq ft. Textured or porous surfaces drop to 200–250 sq ft per gallon. The label always lists the manufacturer's coverage spec — read it before estimating.
- Smooth primed drywall:350–400 sq ft/gal. The benchmark coverage for most calculations.
- Bare or patched drywall:250–300 sq ft/gal. Use a primer first — bare drywall absorbs paint at 2× the rate of primed drywall.
- Textured drywall (orange peel, knockdown): 300–350 sq ft/gal. Light textures barely affect coverage; heavy ones (popcorn ceilings) cut it 30–40%.
- Smooth wood (interior trim): 350 sq ft/gal. Latex bonds well over a primed wood surface.
- Masonry (brick, concrete, block): 150–250 sq ft/gal first coat. Always seal/prime first.
How Many Coats Do I Need?
Two coats is the universal standard for a quality finish. One coat is acceptable when re-coating the same color over a recently painted surface and your paint claims “one-coat coverage.” Three coats are typical for major color changes (deep to light, dark to white) or when going over heavy stains and patches.
The instinct to skip the second coat is always a mistake on a new paint job. Even a perfectly applied first coat reads slightly translucent in raking light or in lighter colors. Two coats is the minimum for a finish that doesn't age poorly.
Do I Need to Prime First?
Use primer for bare drywall, bare wood, large color changes (especially deep to light), patched repair work, glossy surfaces, and stained surfaces. Skip primer when re-coating an existing painted surface in a similar color and finish. Paint-and-primer-in-one products perform well over existing paint but still need a separate primer on bare or stained substrates.
Are 5-Gallon Buckets Cheaper Than 1-Gallon Cans?
Yes — 5-gallon buckets typically save $5–15 per gallon vs buying five separate 1-gallon cans of the same paint. For projects over 4 gallons, the bucket is the clear win. Below 4 gallons, individual cans give more flexibility for color matching and let you return unused product at most retailers.
How Much Paint for a 1,000 Sq Ft Exterior?
For 1,000 sq ft of exterior wall surface (a typical 25×40 single-story house), plan on 3–4 gallons for a single coat or 6–8 gallons for two coats of premium exterior latex. Add 10–15% extra for textured siding (lap, board-and-batten, T1-11). Trim, doors, and shutters get separate gallons in their accent colors.
How Long Should Paint Dry Between Coats?
Latex dries to touch in 30–60 minutes and re-coats in 2–4 hours; oil-based takes 6–8 hours between coats. Always read the can — humidity, temperature, and ventilation extend dry times significantly. Re-coating too early causes lifting and a soft finish; waiting too long with some products creates bonding issues. Most pros do two coats in one working day.
How Much Paint for Common Room Sizes?
Pre-calculated gallon needs for typical rooms with 8-ft ceilings, ceiling included, 1 door + 1 window, two coats of standard latex at 350 sq ft/gal:
- 10×10 bedroom — ~2.4 gallons
- 10×12 bedroom — ~2.6 gallons
- 12×12 living room — ~2.83 gallons
- 12×14 master bedroom — ~3.1 gallons
- 14×16 large room — ~3.7 gallons
- 16×20 great room or master — ~4.6 gallons
For walls only (no ceiling), subtract roughly 0.4–1.0 gallons per room depending on size.
Cost varies by region. The Estimated Material Cost card pulls from our indicative national-average pricing dataset(refreshed quarterly). Northeast and California metros run 15–40% above the national midpoint while Midwest and Southeast metros run 5–15% below — verify locally for binding quotes.
How Much Does Mid-Grade Interior Latex Paint Cost?
Mid-grade interior latex paint averages about $32.00 per gallon nationally as of our April 2026 research. Acrylic latex interior. Regional variation is significant — Northeast and California metros run 15–40% above the national midpoint while Midwest and Southeast metros run 5–15% below. See our pricing methodology for sources and confidence tiers.
Related Calculators
- Drywall Calculator — Sheets and square feet for the substrate
- Concrete Calculator — Slabs and footings for the structural side
- Deck Board Calculator — Boards and linear feet for outdoor staining
Written by Daniel McCarney — AceCalc