Paint Calculator
- Materials
- Labor
- Profit
Primer is extra: bare drywall and big color changes usually need a coat of primer first.
Turn this into a quote
A one-page PDF for your customer, filled in from the numbers above. Your markup isn't shown.
How the paint calculation works
Measure the walls, then take out doors and windows
Wall length × height gives the wall area. A 12 × 10 ft room with 8 ft walls is 44 × 8 = 352 sq ft; one door and two windows take off about 50 sq ft.
Multiply by the number of coats
Two coats is the norm for a color change or fresh drywall. One coat can do for a refresh in the same color.
Divide by the coverage on the can
Most interior paint covers 350–400 sq ft per gallon on smooth walls. Rough, porous or unprimed surfaces soak up more, so plan on 250–300.
Round up to whole gallons and price the job
Add 10% for waste and touch-ups, round up, and multiply by the price per gallon. Then add labor hours and your markup to get the number to put on the quote.
Worked example. A 12 × 10 ft room with 8 ft walls has 352 sq ft of wall. Minus one door and two windows (50 sq ft) leaves 302 sq ft. Two coats plus 10% waste is 664.4 sq ft, which at 350 sq ft per gallon is 1.9 gallons, so you buy 2 gallons for $90. Add 8 hours of labor at $50 ($400) and a 25% markup ($122.50) and the price to quote is $612.50, or $2.03 per sq ft of wall painted.
Paint FAQ
How much does interior painting cost per square foot?
Divide the full price (paint, labor and markup) by the square feet of wall you paint. The calculator shows it as the price per sq ft painted. Your labor rate, the number of coats and prep work matter most, so work it out from your own numbers.
How much paint do I need for a room?
For a typical 12 × 10 ft bedroom with 8 ft walls, about 2 gallons for two coats on the walls. Add roughly another gallon if you also paint the ceiling.
How many square feet does a gallon of paint cover?
Usually 350–400 sq ft per coat on smooth, previously painted walls. Textured, bare or porous surfaces can drop to 250–300 sq ft, so check the label for the product you use.
How do I calculate paint by square feet?
Multiply the paintable square feet by the number of coats, then divide by the coverage per gallon. 302 sq ft × 2 coats ÷ 350 = 1.7 gallons before waste.
How much should I charge to paint a room?
Estimate the hours, including prep, masking and cleanup, and multiply by your rate (or use a labor price per sq ft). Add paint and supplies, then your markup for overhead and profit. With $90 of paint, 8 hours at $50 and a 25% markup, the 12 × 10 ft room is $612.50, about $2.03 per sq ft of wall painted.
Do I need two coats of paint?
Two coats give even color and hide roller marks, and they are standard for color changes and new drywall. One coat can be enough when repainting the same color over a sound surface.
How much paint do I need for the exterior of a house?
Use the same method: the house perimeter × wall height plus gable triangles, minus doors and windows, times coats, divided by coverage. Siding and stucco often cover only 250–300 sq ft per gallon.