Paint Calculator

Calculate exactly how much paint you need for your project. Enter room dimensions or wall area, subtract doors and windows, and get accurate gallon estimates with cost breakdowns.

Gross wall area: 352 sq ft
Subtract Openings

Paintable area for this room

352 sq ft

Paint Settings

Results

Total Paintable Area

352 sq ft

Area with 2 Coats

704 sq ft

Paint Needed

2 gallons

Estimated Cost

$105

Purchase Options

Gallons OnlySimple

3 gallons

$105 total

Gallons + QuartsLess Waste

2 gals + 1 qt

~$80.5 total

Quick Reference: Coverage by Surface

Smooth Drywall

350-400 sq ft/gal

Textured Drywall

250-300 sq ft/gal

Bare Wood

300-350 sq ft/gal

Stucco

150-250 sq ft/gal

Brick

150-200 sq ft/gal

Concrete Block

150-200 sq ft/gal

Metal

350-500 sq ft/gal

Previously Painted

350-400 sq ft/gal

Common Room Sizes

Small Bedroom

10 x 10 ft, 8 ft ceiling

320 sq ft

wall area

Average Bedroom

12 x 12 ft, 8 ft ceiling

384 sq ft

wall area

Large Bedroom

14 x 16 ft, 8 ft ceiling

480 sq ft

wall area

Living Room

15 x 20 ft, 8 ft ceiling

560 sq ft

wall area

Bathroom

8 x 10 ft, 8 ft ceiling

288 sq ft

wall area

Kitchen

12 x 14 ft, 8 ft ceiling

416 sq ft

wall area

How to Use the Paint Calculator

Start by adding your rooms. For each room, enter the length, width, and ceiling height to automatically calculate wall area, or switch to Manual mode if you already know the total wall area. Add any doors and windows to subtract their area from the total. The calculator accounts for multiple coats and your paint's coverage rate to give you the exact number of gallons needed.

Paint Coverage by Type

Paint TypeCoverage (sq ft/gal)Best For
Flat / Matte Latex350 - 400Ceilings, low-traffic rooms
Eggshell Latex350 - 400Living rooms, bedrooms
Satin Latex350 - 400Kitchens, bathrooms, hallways
Semi-Gloss Latex350 - 400Trim, doors, cabinets
High-Gloss300 - 350Trim, furniture, accents
Oil-Based / Alkyd350 - 450Trim, cabinets, high-wear areas
Primer (Latex)200 - 300New drywall, color changes
Primer (Shellac/Oil)200 - 300Stain blocking, odor sealing

Surface Preparation Tips

  • Clean walls with a damp cloth or TSP solution to remove dust, grease, and grime before painting.
  • Fill nail holes and cracks with lightweight spackle. Sand smooth once dry.
  • Sand glossy surfaces lightly (120-150 grit) to help new paint adhere.
  • Apply painter's tape to trim, ceiling edges, and any areas you want to protect.
  • Use a stain-blocking primer on water stains, smoke damage, or when switching from dark to light colors.
  • Prime bare drywall, wood, or patched areas. These porous surfaces absorb more paint without primer.
  • Allow primer and each coat of paint to dry fully (typically 2-4 hours for latex) before applying the next coat.

Frequently Asked Questions

How much paint do I need for a 12x12 room?+
A 12x12 room with 8-foot ceilings has about 384 sq ft of wall area. After subtracting a door (~21 sq ft) and a window (~15 sq ft), you have roughly 348 sq ft of paintable surface. With 2 coats and standard coverage of 350 sq ft/gallon, you need about 2 gallons of paint.
How many square feet does a gallon of paint cover?+
A gallon of interior latex paint typically covers 350-400 sq ft per coat on smooth surfaces. Textured walls, unpainted drywall, or porous surfaces may reduce coverage to 200-300 sq ft per gallon. Premium paints sometimes offer higher coverage, around 400+ sq ft per gallon.
Should I buy gallons or quarts of paint?+
Gallons are more cost-effective per unit volume. A quart typically costs about 30% of a gallon price but only contains 25% of the paint. Buy gallons for large areas and quarts only for small touch-ups or accent walls under 100 sq ft. This calculator shows you the optimal combination.
How do I calculate paint for a room with vaulted ceilings?+
For vaulted or cathedral ceilings, use the Manual mode in this calculator. Measure each wall individually, calculate the area of triangular or trapezoidal walls (base x average height), then enter the total wall area. Remember to subtract doors and windows as usual.
Do I need to account for primer separately?+
Yes. Primer coverage differs from paint, typically 200-300 sq ft per gallon. If painting over dark colors, new drywall, or stained surfaces, add a coat of primer before your paint coats. Some paint-and-primer combos may eliminate this step, but separate primer gives better results on problem surfaces.
How much extra paint should I buy?+
Buy 10-15% more paint than calculated to account for touch-ups, mistakes, and future repairs. This calculator rounds up to the nearest gallon, which typically provides that buffer. Keep leftover paint sealed and stored for future touch-ups, as exact color matching later can be difficult.
How do I estimate paint for textured walls?+
Textured walls absorb more paint. For light texture, reduce coverage to about 300 sq ft/gallon. For heavy texture like stucco or popcorn, use 200-250 sq ft/gallon. Adjust the coverage rate field in this calculator to match your wall texture for more accurate estimates.

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