1. Select your shape
Choose from rectangle, circle, triangle, trapezoid, L-shape, annulus, or wall-and-window layouts to match your project.
What is paint square footage?
Paint square footage is the total wall surface area that needs to be painted, measured in square feet. To find paint square footage, multiply wall height by wall width for each wall, then subtract window and door areas. Paint square footage determines how many gallons of paint to buy for your project.
Getting started
How to Calculate Square Footage for Paint
To calculate square footage for paint, measure each wall (height x width), add all wall areas together, then subtract window areas (typically 15 sq ft each) and door areas (typically 21 sq ft each). One gallon of paint covers approximately 350-400 square feet with one coat.
2. Enter your measurements
Input dimensions in feet, inches, yards, meters, or centimeters. The Square Foot Calculator converts units automatically.
3. Get area and cost
View results in square feet, square yards, square meters, and acres. Add a material price per unit to estimate total project cost.
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
Enter the price per square foot of material to estimate total cost. The calculator accepts pricing in square feet, square inches, square yards, or square meters and converts to the correct total based on your area.
There are 2 steps to calculate material cost:
- Enter the price per unit area. For tiling projects, enter the price per box and the number of square feet each box covers. For carpet, enter the cost per square yard. For flooring installation with hardwood or laminate, enter the cost per square foot.
- Select the unit of area that matches your pricing. The Square Foot Calculator multiplies your total area by the unit price to produce an estimated material cost, including labor costs when added to the per-unit price.
To calculate the volume of bulk materials like mulch or gravel for landscaping, convert area to cubic yards or cubic meters by multiplying the area by the depth of material.
Core formula
Basic Formula for Area
Area is the amount of space occupied by a 2-dimensional shape. The shape could be a floor, a wall, a playground, or a field. The simplest formula for area applies to any rectangular shape:
Area = Length × Width
Measure the length and width of the space in feet. Multiply the two values to get the area in square feet. A rectangular room that is 12 feet (3.66 meters) long and 10 feet (3.05 meters) wide has an area of 120 sq ft (11.15 sq m).
Square yardage is area measured in yards, and square meters is area measured in meters. Measure in feet, find the area in square feet, then convert to the unit you need.
For an L-shape room, split the floor into 2 rectangular sections, calculate each area, and add the results. Convert all measurements to the same unit before multiplying, if your dimensions are in different units like inches and feet.
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.
Waste factor
Adding 10% Surplus for Materials
Add a 10% surplus to your calculated area to account for material waste during cutting, breakage, and pattern matching. This waste factor applies to flooring, carpet, tiling projects, and landscaping materials.
Original Area
100 sq ft
+10%
Order Amount
110 sq ft
Total Material = Area × 1.10
A room with 200 sq ft of floor area needs 220 sq ft of material: 200 × 1.10 = 220 sq ft. Increase the surplus to 15% (multiply by 1.15) for diagonal flooring installation patterns or complex tiling projects with many cuts. The Square Foot Calculator includes a waste factor field for this calculation.
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.