Paint Calculator

Calculate how much paint you need for walls, ceilings, and trim.

ft
ft
ft
sq ft
Gallons Needed
2
2 cans to buy
Total Wall Area
352 sq ft
Paintable Area
307 sq ft
Ceiling Area
0 sq ft
Estimated Cost
$70.00

How to Use This Paint Calculator

  1. Enter your room dimensions — measure the length, width, and height of the room you plan to paint. For irregular rooms, break them into rectangular sections and calculate each separately.
  2. Choose the number of coats — two coats is the standard recommendation for most interior painting projects.
  3. Set the paint coverage — 350 sq ft/gallon is the industry average for smooth drywall. Reduce this number for textured surfaces.
  4. Enter doors and windows — the calculator deducts approximately 21 sq ft per door and 12 sq ft per window from the total paintable area.
  5. Check the ceiling box if you plan to paint the ceiling as well. The ceiling area will be added to the total.

Understanding Paint Coverage

Paint coverage depends on several factors including surface texture, paint quality, and application method. A gallon of premium interior latex paint covers approximately 350 to 400 square feet on smooth drywall with a roller. However, coverage can vary significantly based on conditions.

Coverage by Surface Type

Smooth drywall offers the best coverage at 350-400 sq ft per gallon. Lightly textured walls reduce coverage to about 300-350 sq ft. Heavily textured surfaces like stucco or popcorn ceilings may only yield 200-300 sq ft per gallon. Bare wood and previously unpainted surfaces absorb more paint, typically covering only 250-350 sq ft per gallon.

The Paint Coverage Formula

This calculator uses the following formula to determine paint needed:

Wall Area = 2 × (Length + Width) × Height
Paintable Area = Wall Area - (Doors × 21) - (Windows × 12) + Ceiling
Gallons = ⌈(Paintable Area × Coats) ÷ Coverage⌉

Paint Types and When to Use Them

Flat/Matte paint hides imperfections well and is ideal for ceilings and low-traffic rooms. Eggshell provides a subtle sheen and is the most popular choice for living rooms and bedrooms. Satin resists moisture and stains, making it perfect for kitchens, bathrooms, and children's rooms. Semi-gloss and gloss finishes are durable and easy to clean, best for trim, doors, and cabinets.

Do You Need Primer?

Primer is essential when painting over bare drywall, wood, or masonry for the first time. It creates a uniform base that helps paint adhere properly and provides true color. Primer is also necessary when making dramatic color changes (especially covering dark colors with light ones), covering stains or water damage, and painting over glossy surfaces. Modern paint-and-primer products can work for recoating similar colors in good condition, but a separate primer coat always gives better results on problem surfaces.

Tips for Accurate Estimates

Always buy slightly more paint than calculated. The standard recommendation is to add 10-15% for touch-ups, cutting in around edges, and primer if needed. Keep leftover paint for future touch-ups — store cans upside down to create a tight seal. If you are painting accent walls or multiple colors, calculate each color separately using the measurements for those specific walls.

Frequently Asked Questions

A single gallon of paint typically covers about 350 to 400 square feet of smooth surface with one coat. Rough or textured surfaces like stucco or brick may reduce coverage to 200-300 square feet per gallon. Always check the manufacturer's label for the specific product you're using.
Primer is recommended when painting over bare wood, drywall, or a dark color with a lighter one. Many modern paints include a built-in primer (paint-and-primer-in-one), which works well for repainting walls that are in good condition with a similar color. For best results on new surfaces or dramatic color changes, use a separate primer coat.
Most paint jobs require two coats for even coverage and full color. A single coat may be sufficient when repainting the same color. Three coats may be needed when covering very dark colors with light ones, using very light or bright colors, or painting over patched areas.
Painting the ceiling can make a room feel fresher and more complete. Ceilings should be painted if they show stains, yellowing, or if you're changing the wall color dramatically. Use a flat/matte ceiling paint to minimize imperfections. A white or off-white ceiling makes rooms feel taller and brighter.
For L-shaped or irregular rooms, break the room into rectangular sections and calculate each section separately. Measure each wall individually, sum the total wall area, then subtract doors and windows. You can use this calculator multiple times for each section and add the totals together.