10 ft by 12 ft room
A 10 by 12 room is 120 square feet. For flooring with 10 percent waste, buy about 132 square feet.
Square Footage Calculator
Accurate square footage keeps you from under-buying, over-buying, or mixing material batches mid-project.
Square Footage Examples
12 ft by 15 ft room
A 12 by 15 room is 180 square feet. For tile with 15 percent waste, buy about 207 square feet.
Paint for a 10 ft by 12 ft room
With 8 foot ceilings, the gross wall area is about 352 square feet before subtracting doors and windows.
Core Formulas
- Rectangle area = length x width
- Wall area = room perimeter x wall height
- Material to buy = measured area x waste factor
- Split irregular rooms into rectangles and add them together
Waste Factors
- 10 percent for most straight flooring layouts
- 15 percent for diagonal tile or patterned installs
- Extra material for repairs when dye lots or finishes may change
Common Questions
How do you calculate square footage?
For a rectangle, multiply length by width. For irregular rooms, split the shape into rectangles, calculate each area, and add them together.
How much extra material should I buy?
For most flooring or tile projects, add 10 percent waste for straight layouts and 15 percent for diagonal or patterned layouts.
How do you calculate wall square footage for paint?
Multiply the room perimeter by wall height, then subtract doors and windows. Multiply by the number of coats to estimate paint coverage.
Plan This Project in ChatDIY
ChatDIY can help you calculate room area, wall area, waste factor, and material quantities for your exact project.