Painting & Wallpapering/Paint calculation


Hello Ed,

We're painting the house inside. The walls are flat, no texture, and they're currently painted off-white. We're going to paint them white on top (2 coats)

We're going to use PPG High-Hide paint, and for the ceilings Home Depot's BEHR ceiling paint

How can we calculate how much paint we need per square feet for the walls and for the ceiling? Is there a formula?

Thanks in advance.

Best regards,


Figure the square feet of the walls.
Ecample is a 12 foot by 12 foot room.
with 8 foot walls.

Ceiling 12 by 12 equals 144 square feet.
1 12 by 8 foot wall equals 96 square feet 1 wall 8'x 12'=96 square feet.
4 walls =  ( 96x4 ) = 384 square feet.
Subtract 15 square feet for each door and window .
If there is one door and two windows.
384 square feet subtract 45 square feet = 339 square feet.
So 339 square feet for the walls + 144 square  feet  for the  ceiling =483 square feet  for 1 coat.
483 x2= 966 square feet.
Paint covers 300 square feet per coat.
So in that example with two coats you'll need between so in that example you will need between 3 & 4 gallons you will need me we can
I'd probably start off at 3 gallons
To put it simply what I do is figure 300 square feet per coat per gallon.  

Painting & Wallpapering

All Answers

Answers by Expert:

Ask Experts


Ed Kuchar


I've been a wallpaperhanger for 40 years. I've been a house painter (interior and exterior) for 38 years. I also do wallpaper removing and wall patching and light skim coating. I can answer any questions concerning: patching and wall preparation for painting or wallpaper, different types of paint, or wallpaper, what type to use for your job. questions about wallpaperhanging & painting how to measure an area for paint or wallpaper. questions concerning different types of wallpaper general questions on how to hang wallpaper (what type of paste, tools, etc.


I have my own wallpapering and painting business. Blue Sky Paperhanging & Painting Inc. I've been doing paperhanging & painting for 30 years. Most of my experience is in residential and not commercial.

Better Business Bureau.

I did the wallpaperhanging on the movie set "My Own Private Idaho" 1991.

I learned how to hang wall paper and wallcoverings at the West Valley Occupational School in Van Nuys California in 1978.

©2017 All rights reserved.