Paint Calculator – Gallons, Labor Hours & Total Cost

A standard 12×14 room with 9-foot ceilings has about 468 sq ft of wall area. Subtract two doors (40 sq ft) and two windows (30 sq ft) and you're left with roughly 398 sq ft. At 400 sq ft per gallon for smooth drywall, one coat needs 1 gallon. Two coats — which pros always recommend for full coverage — needs 2 gallons. A typical mid-range paint like Sherwin-Williams SuperPaint runs $55/gallon, so materials alone cost $110–$165 including a quart of touch-up paint.

Manufacturers rate most interior latex paints at 350–400 sq ft per gallon on smooth, previously painted drywall. Real-world coverage is lower: expect 300 sq ft/gal on textured or orange-peel surfaces, and 150–200 sq ft/gal on rough masonry or bare wood. Always use the conservative estimate so you don't run short mid-wall — running out of paint mid-job is the #1 avoidable mistake on DIY projects.

One coat works only when you're repainting the exact same color with a high-hide paint. For color changes, new drywall, or light-over-dark, two coats are essential. Skipping the second coat leaves the finish patchy and transparent under raking light. Premium paints like Benjamin Moore Aura or Sherwin-Williams Emerald are marketed as "one coat coverage" — they genuinely are for same-color touch-ups, but most pros still apply two coats on full repaints for durability.

Use primer when: (1) painting new uncoated drywall — the paper face absorbs paint unevenly without primer; (2) going from a dark to a light color; (3) covering water stains, smoke damage, or crayon marks; (4) painting over glossy or oil-based paint with latex. Skip primer when: repainting with a similar color on clean, already-painted walls in good condition — a high-quality paint-and-primer-in-one is sufficient. Standard drywall primer runs $25–$35/gal at big-box stores.

A professional painter can roll and cut in a standard 12×14 room in about 3–4 hours per coat, including prep (taping, laying drop cloths, moving furniture). Two coats plus prep = 7–9 hours total. DIYers typically take 1.5–2× longer. Our calculator uses 150 sq ft/hr as the painting productivity rate and 0.005 hours per sq ft for prep — consistent with PDCA (Painting & Decorating Contractors of America) industry estimates.

Professional painter rates in the US range from $1.50 to $3.50 per sq ft for standard interior walls, all-in (labor + paint). Budget painters in low-cost-of-living areas may quote $1.00–$1.50/sq ft; premium painters in NYC, SF, or Boston charge $4.00–$7.00/sq ft. The painter's hourly wage (BLS median: $23.40/hr) is only part of the cost — the contractor adds overhead, insurance, and profit, bringing the effective billing rate to $45–$75/hr.

Flat/matte: hides imperfections best, zero sheen — ideal for ceilings and low-traffic bedroom walls. Eggshell: slight sheen, easy to wipe, best for living rooms and hallways. Satin: noticeably shiny, moisture-resistant, the standard for kitchens and bathrooms. Semi-gloss: high sheen, very washable, used on trim, doors, and cabinets. Gloss: maximum durability, used on furniture and exterior trim. Note: the calculator's gallon count is the same regardless of sheen; sheen doesn't affect coverage.

Always buy gallons if you need more than 1.5 quarts — a quart ($15–$25) is only 25% of a gallon's volume but costs 35–45% as much per unit. The exception: touch-up paint. Keep one quart of your wall color stored in a cool, dark place for future touch-ups — dried paint on roller marks looks different from a freshly opened can, so having a true color match matters. Most paint stores let you get a quart mixed from the same formula for $15–$20.