The Ceiling Paint calculator computes the number of gallons of paint and primer needed to cover a ceiling (light grey in diagram) of a rectangular room based on the length and width of the room. 
INSTRUCTIONS: Choose units and enter the following:
- (L) Length of Room
- (W) Width of Room
- (PC) Coverage per Gallon (area covered by one gallon: default 400ft2)
- (CT) Coats of Paint
Ceiling Paint (CP): The calculator computes the number of gallons or quarts of paint or primer needed for the ceiling. Note, gallons and quarts can be automatically converted into other volume units via the pull-down menu.
The Math / Science
The surface area of a ceiling (light blue in diagram) is based on the length and width of the room. The mean square feet for a gallon of quality paint is 400 ft2 . Primer covers 200 ft2. Note: many paints no longer require primer. The gallons of paint and primer are the total surface area divide by the square feet per gallon.
Paint Cost Survey Data
One should use the pricing for paint or primer that can be bought locally since prices may vary. However, the following prices are recent U.S. dollar costs for different price ranges of one gallon of paint and primer in the United States:
- Paint Pricing Survey date: 7/29/22
- Paint Price Survey Source (online): HomeDepot
- Price of premium (high quality) paint: $61.94 USD
- Price of medium grade paint: $48.98 USD
- Price of economy paint: $26.98 USD
- Price of primer: $19.98 USD
Wall and Room Calculators
- Number of gallons to paint or primer a room.
- Cost to paint or prime a room.
- Surface area of the interior walls of a room
- Surface area of the interior walls and ceiling of a room.
- Floor area of a room
- Volume of a room
- Energy (BTUs/hr) needed to heat a room
- Number of Studs in a Room
- Number of drywall sheets needed for a room
- Surface area of a Wall
- Surface Area of a Ceiling