Paint Calculator — How Much Paint Do You Need? (2026)
Accurately calculate required paint gallons, liters, and can breakdowns (1-gal, 5-gal, and quarts) with custom door and window deductions.
Project Inputs & Specs
Visual Blueprint & Diagram
Estimated Paint Needed
Equivalent to 8.57 Liters for 2 coat(s)
Buy 2 × 1-Gallon Can(s) + 2 × Quart Can(s)
5-gallon buckets offer up to 20-30% bulk savings per gallon. Always retain a half-quart of leftover paint in an airtight mason jar for future wall scuff touch-ups.
Paint Volume Formula & Surface Deductions
To calculate net paintable wall surface, compute total perimeter area and deduct openings for doors and windows before applying coat multipliers:
Wall Area = [2 × (Length + Width) × Height] - (Doors × 21 sq ft) - (Windows × 15 sq ft) | Gallons = (Net Area × Coats) ÷ Coverage RateStep-by-Step Step Rule:
- 1Measure room length, width, and ceiling height.
- 2Calculate total gross perimeter wall area.
- 3Subtract standard door openings (approx. 21 sq ft each) and window openings (approx. 15 sq ft each).
- 4Multiply net wall area by desired coat count (2 coats recommended for full opacity and durability).
- 5Divide total square footage by manufacturer coverage rating (standard is 350 sq.ft per US gallon).
How Much Paint Do You Need? Room Square Footage & Can Sizing Guide
Estimating paint volume accurately prevents mid-project hardware store runs and eliminates expensive leftover paint cans stored in closets. One standard US gallon of interior latex paint covers 350 to 400 square feet (32.5 to 37 m²) on smooth drywall, but drops to 250 to 300 sq.ft over unprimed or textured plaster.
Paint Sheen Selection & Durability Chart
| Paint Finish / Sheen | Light Reflectivity | Recommended Room Locations |
|---|---|---|
| Flat / Matte (0-5% gloss) | Non-reflective | Ceilings, master bedrooms, low-traffic formal living rooms. Hides drywall bumps. |
| Eggshell (10-25% gloss) | Soft velvety luster | Most popular choice for standard living rooms, hallways, dining rooms, and home offices. |
| Satin (25-35% gloss) | Silky pearl sheen | High-moisture & high-touch areas: kitchens, bathrooms, kids bedrooms, laundry rooms. |
| Semi-Gloss (35-70% gloss) | High shine & washability | Baseboards, crown molding, interior doors, window casings, cabinetry. |
When Is a Primer Coat Mandatory?
Even with modern “paint and primer in one” formulas, professional painters apply a standalone primer under these conditions:
- New Bare Drywall: Raw drywall paper and spackle joints absorb moisture unevenly, causing “flashing” (dull blotches) without PVA primer sealer.
- Dark to Light Color Shifts: Transitioning from navy blue, red, or dark brown to white requires 1 coat of gray-tinted primer to prevent 4+ topcoats.
- Stain Blocking: Water damage, smoke soot, and wood tannins require an oil-based or shellac-based stain-blocking primer (e.g. Zinsser BIN or Kilz).
Frequently Asked Questions (FAQ)
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