The starting point for nearly every estimate: floor or wall area in square feet. Multiply length by width for rectangles, and add or subtract rectangles for L-shapes and openings.
The example
A 14 × 12 ft room.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | 14 × 12 | — |
| 3 | Area | → 168 ft² |
The formula
The formula:
How it works
How it works:
- For a rectangle, area = length × width in feet.
- For an L-shape, split it into rectangles and add the areas.
- Subtract openings (closets out, or windows/doors for wall paint) as needed.
- Convert inches to feet first (÷12) so all measurements share the same unit.
Wall area for paint/wallpaper: add the perimeter × ceiling height, then subtract door and window areas. =(2*(L+W)) * height - openings. For flooring you want the floor footprint (L×W); for wall coverings you want the wall area — don’t mix them up.
Try it: interactive demo
Length and width (feet).
Variations
L-shaped room
Add rectangles:
Wall area
Perimeter × height:
Inches to feet
Convert first:
Pitfalls & errors
Same units. Convert everything to feet before multiplying.
Floor vs wall. Flooring uses footprint; paint uses wall area — different numbers.
Split irregular shapes. Break L-shapes into rectangles and add.
Practice workbook
Frequently asked questions
How do I calculate square footage in Excel?
How do I handle an L-shaped room?
How do I find wall area for painting?
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