1. Measure walls and ceilings
Measure height and width of each wall in feet. Multiply for wall area.
What is paint square footage?
Paint square footage is the total wall and ceiling area receiving paint. Measure height × width of each wall and sum the areas. Subtract doors and windows from the total — the wall with window calculator handles this automatically.
Getting started
How to Calculate Square Footage for Paint
To calculate paint square footage, measure height and width of each wall in feet. Multiply height × width for wall area. Subtract a standard door (21 sq ft) and standard window (15 sq ft) from each wall as needed. One gallon of paint covers 350-400 sq ft per coat.
2. Subtract openings
Subtract doors (21 sq ft each) and windows (15 sq ft each) from total wall area.
3. Convert to gallons
One gallon covers 350-400 sq ft per coat. For 2 coats, divide square footage by 175-200 to get gallons.
Quick reference
Reference
1 acre = 43,560 square feet
1 square yard = 9 square feet
1 square meter = 10.764 square feet
1 square inch = 0.00064516 square feet
Material pricing
Calculate Cost of Materials
Quality interior paint costs $25-50 per gallon. Multiply gallons needed by price per gallon for total paint cost.
There are 2 steps to calculate material cost:
- Enter the price per gallon of paint and the coverage in square feet per gallon (typically 350-400).
- The Square Foot Calculator divides wall area by gallon coverage and multiplies by price for paint cost.
A 1,500 sq ft home interior needs 6-8 gallons for one coat or 12-15 gallons for two coats. Buy 1 extra gallon for touch-ups.
Calculating Square Footage for Walls
Measure the wall width and the wall height in feet. Multiply the width by the height to get the total wall area in square feet. Subtract the area of any doors or windows to find the exact paint coverage required. A wall that is 12 feet wide and 8 feet tall has a total area of 96 sq ft. A 3 ft × 4 ft window removes 12 sq ft, leaving 84 sq ft of paintable surface.
To subtract multiple windows of the same size from one wall, multiply the window width by the number of windows. Enter the total as the window width in the Square Foot Calculator. Height remains the height of one window.
FAQ
Frequently Asked Questions
How do I calculate wall square footage for paint?
Multiply wall height by wall width for each wall, add them together, then subtract window and door areas. A 12x8 ft wall minus a 3x5 ft window = 96 - 15 = 81 sq ft of paintable surface.
How much paint do I need per square foot?
One gallon of paint covers 350-400 square feet per coat. For a room with 400 sq ft of wall area needing two coats, you need approximately 2-2.3 gallons of paint.
How do I calculate paint for a room with 4 walls?
Calculate each wall (height x width), add all four areas, subtract windows and doors. A 12x10 ft room with 8 ft ceilings has about 352 sq ft of wall area (2x96 + 2x80), minus openings.
How many square feet does a gallon of paint cover?
One gallon covers 350-400 sq ft with one coat on smooth surfaces. Textured walls, porous surfaces, and dark-to-light color changes may require more paint, reducing coverage to 250-300 sq ft per gallon.
Should I subtract windows and doors from paint area?
Yes, subtract all openings. A standard window is about 15 sq ft (3x5 ft) and a standard door is about 21 sq ft (3x7 ft). This prevents buying excess paint.
How do I calculate paint for a ceiling?
Multiply room length by room width for ceiling area. A 12x10 ft room has a 120 sq ft ceiling. One gallon of ceiling paint covers 350-400 sq ft, so one gallon handles most single rooms.
REFERENCES
Further Reading & References
Trusted external sources and related sections on this site. External links open authoritative references on Wikipedia and government agencies.
Explore this Square Foot Calculator site
Authoritative external references
- WIKIPaint — Wikipedia
- WIKIInterior design — Wikipedia
- GOVEPA: Lead Paint Safety