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Paint Calculator

Calculate how much paint you need for any room. Get gallon estimates, account for doors and windows, and estimate costs.

Paint Worksheet
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How to Calculate Paint Needed

Measure wall area, subtract doors and windows, divide by coverage rate, then multiply by number of coats. This calculator handles it automatically.

Step by Step

  1. Calculate wall area: For rooms with 8-foot ceilings, multiply the room perimeter (in feet) by 8
  2. Subtract openings: Deduct 21 sq ft per door and 15 sq ft per window
  3. Divide by 350 (sq ft per gallon) to get gallons per coat
  4. Multiply by 2 (most jobs need two coats)
  5. Round up to the nearest gallon

Example: 12×14 Room

  • Perimeter: 2 × (12 + 14) = 52 feet
  • Wall area: 52 × 8 = 416 sq ft
  • Minus 1 door (21 sq ft) and 2 windows (30 sq ft) = 365 sq ft
  • At 350 sq ft/gallon × 2 coats = 2.1 gallons → buy 3 gallons

Paint Coverage Rates

  • Interior paint (smooth walls): 350-400 sq ft per gallon
  • Textured walls: 250-300 sq ft per gallon (20-30% reduction)
  • Primer: 200-300 sq ft per gallon
  • Exterior paint: 250-350 sq ft per gallon

When You Need More Coats

  • 2 coats: Standard for most projects, even with "one-coat" paint
  • 3 coats: Dark-to-light color changes, covering reds/oranges/yellows
  • Primer + 2 coats: New drywall, bare wood, or dramatic color changes. A tinted primer saves paint and money

Choosing the Right Paint

  • Flat/matte: Hides imperfections, best for ceilings and low-traffic rooms. Hardest to clean
  • Eggshell: Slight sheen, good for living rooms and bedrooms. Easy to wipe
  • Satin: Moderate sheen, durable. Best for kitchens, bathrooms, hallways
  • Semi-gloss: Highly washable. Best for trim, doors, cabinets, and high-moisture areas

Pro Tips

  • Buy all paint from the same batch number to ensure consistent color
  • Keep leftover paint for touch-ups — matching colors later is difficult
  • Higher-quality paint ($40-60/gallon) covers better and lasts longer than budget paint, often saving money by requiring fewer coats
  • Use a tinted primer when changing colors significantly — it costs $25-35/gallon but can eliminate an entire coat of expensive topcoat

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On conv.awajis.com

Square Feet to Square Meters Convert wall area to metric.

Frequently Asked Questions

How much paint do I need for a room?

A 12 by 12 ft room with 8 ft walls needs about 1 gallon of paint per coat, or 2 gallons for two coats. Wall area is 2 x (length + width) x height, here 384 sq ft. Subtract about 21 sq ft per door and 15 sq ft per window, then divide by 350 sq ft per gallon.

How much does a gallon of paint cover?

One gallon of paint covers about 350 to 400 sq ft on smooth surfaces in a single coat. Textured walls may need 20 to 30% more paint, because the uneven surface has more area to fill. Divide the wall area by 350 to estimate gallons per coat, then multiply by the number of coats.

How many coats of paint do I need?

Most painting jobs need 2 coats. Use 3 coats when covering a dark color or putting a light color over a dark one. Apply primer first on new drywall, bare wood, stain-prone surfaces, or for a dramatic change from dark to light, because primer seals the surface and improves adhesion.

How much paint do I need for a ceiling?

Ceiling area is room length times width, and one gallon covers about 350 sq ft per coat. A 12 by 12 ft ceiling is 144 sq ft, which needs less than half a gallon per coat. Ceilings and trim are separate purchases from wall paint, since trim usually uses a different sheen and formula.