Home › Paint Calculator

Paint Calculator

Find out exactly how much paint you need for any room. Enter your dimensions, doors, and windows — get gallons, cans, and a cost estimate instantly.

🎨 Calculate Your Paint

ft
ft
ft
sq ft/gal
$/gal
Wall Area
—
sq ft (paintable)
Paint Needed
—
gallons
Cans to Buy
—
gallon cans

🎨 Paint Finish Guide

FinishBest ForSheen
Flat / MatteCeilings, low-traffic rooms0–5%
EggshellLiving rooms, bedrooms10–25%
SatinKitchens, bathrooms, hallways25–35%
Semi-GlossTrim, doors, cabinets35–70%
High-GlossAccent pieces, furniture70–90%

💰 Paint Costs (2026)

  • Budget (e.g., Behr Ultra): $25–$35/gal
  • Mid-range (e.g., Benjamin Moore Regal): $45–$65/gal
  • Premium (e.g., Farrow & Ball): $80–$110/gal
  • Primer: $15–$30/gal
  • Ceiling paint: $20–$40/gal
  • Pro labor: $2–$6/sq ft

🛒 Paint Buying Tips

  • Buy all your paint at once — batch colors can vary slightly
  • Keep 1 quart for touch-ups (label with room and date)
  • Round up to the next full gallon — running short mid-wall causes visible lap marks
  • Test a sample quart on the wall before committing — colors look different in your lighting
  • Higher-quality paint covers better, lasts longer, and often needs fewer coats

🖌️ Coverage Factors

  • Smooth drywall: 350–400 sq ft/gal
  • Textured walls: 250–300 sq ft/gal
  • Bare wood/drywall: 250–350 sq ft/gal
  • Brick / masonry: 150–250 sq ft/gal
  • Spraying: Uses 20–30% more paint than rolling

Darker colors over light backgrounds and vice-versa may need an extra coat.

How to Calculate Paint for a Room

Figuring out how much paint you need is straightforward once you know the formula. Here's how professionals estimate paint quantities for any room size, shape, or finish.

Step 1: Measure Your Walls

Measure the length of each wall and the ceiling height. Multiply the perimeter of the room (length + width + length + width) by the wall height. This gives you the total wall area in square feet. For example, a 12×14-foot room with 8-foot ceilings has a perimeter of 52 feet and a total wall area of 416 square feet.

Step 2: Subtract Doors and Windows

A standard interior door is about 21 square feet (3×7 ft). A typical window is about 15 square feet (3×5 ft). Subtract these from your total wall area. Our calculator does this automatically — just enter the count of doors and windows.

Step 3: Factor in Coats

Most paint jobs need two coats for solid, even coverage. If you're painting over a similar color with premium paint, one coat may suffice. Dark-to-light or light-to-dark color changes usually require a primer coat plus two finish coats. Multiply your paintable area by the number of coats to get the total coverage needed.

Step 4: Divide by Coverage Rate

A gallon of interior latex paint covers approximately 350 square feet on smooth walls. Divide your total coverage area by 350 to get the gallons needed. Always round up — running out of paint mid-wall can leave visible lines where you stopped.

When to Use Primer

Primer is essential when painting new drywall, covering stains, switching from oil-based to latex paint, or making dramatic color changes. Tinted primer (tinted to match your finish color) reduces the number of finish coats needed. For most repainting jobs on previously painted walls, a quality paint-and-primer-in-one product works well.

Frequently Asked Questions

How much paint do I need for a 12×12 room?
A 12×12 room with 8-foot ceilings has about 384 sq ft of wall area. After subtracting a door (~21 sq ft) and two windows (~30 sq ft), you have roughly 333 sq ft. At 350 sq ft per gallon, one gallon covers one coat. For two coats, buy 2 gallons. If you're changing colors dramatically, you may need primer plus 2 coats of paint (3 gallons total).
Do I need primer before painting?
Yes, use primer when painting over dark colors, covering stains, painting bare drywall, or switching between paint types (oil to latex). Modern paint-and-primer combos work well for simple color refreshes on previously painted walls. Tinted primer is recommended when making dramatic color changes — it can save you an entire finish coat.
What is the best paint finish for each room?
Flat/matte is ideal for ceilings and low-traffic rooms — it hides imperfections. Eggshell is the most popular finish for living rooms and bedrooms, offering a soft sheen with light washability. Satin works best in kitchens, bathrooms, and hallways due to its moisture resistance. Semi-gloss is perfect for trim, doors, and cabinets. High-gloss is used for accent pieces and furniture.
How much does a gallon of paint cover?
A gallon of paint typically covers 350–400 sq ft on smooth, previously painted surfaces. Rough or textured walls may only get 250–300 sq ft per gallon. Coverage also depends on the paint quality, the color change, and whether you're applying it with a roller (best coverage), brush, or sprayer (uses 20–30% more).
Should I paint the ceiling the same color as the walls?
Most designers recommend painting ceilings flat white or a shade lighter than the walls. This makes rooms feel taller and brighter. Use flat or matte finish on ceilings to hide imperfections — sheen catches the light and highlights every bump. For a dramatic or cozy effect, painting the ceiling a darker color can work in larger rooms with high ceilings.