What Is a Square Footage Calculator?
A square footage calculator finds the total floor area of a room or multiple rooms/sections by multiplying length by width for each, then summing the results — essential for flooring, carpet, tile, or paint estimates.
How to Use the Square Footage Calculator
- Enter the length and width of your room in feet.
- Add additional rooms or sections if needed (e.g., an L-shaped room split into rectangles).
- View your total square footage, plus common waste allowance additions.
Square Footage Formula
Worked Example
Square footage: 12 × 10 = 120 sq ft
With 10% waste allowance: 120 × 1.10 = 132 sq ft to order
Understanding Your Results
Total Square Footage is the raw floor area. Waste Allowance additions account for cuts, mistakes, and pattern matching when ordering flooring, tile, or carpet — most contractors recommend ordering 10% extra for standard installs, and up to 15% or more for diagonal or complex patterns.
Handling Irregular Rooms
For L-shaped or irregular rooms, split the space into simple rectangles, calculate each section's square footage separately, and add them together — this calculator's multi-row feature makes that easy.
Common Mistakes to Avoid
- Forgetting to account for closets, alcoves, or irregular sections that add to (or should be subtracted from) the total area.
- Not ordering enough extra material for waste, cuts, and pattern matching.
- Measuring in inches without converting to feet before calculating.
Frequently Asked Questions
Multiply the room's length by its width (both in feet) to get square feet.
Split the room into two or more rectangles, calculate the square footage of each separately, then add them together for the total.
Most contractors recommend ordering 10% extra for standard rectangular layouts, and up to 15% or more for diagonal patterns or rooms with many cuts and corners.
Divide square feet by 9, since there are 9 square feet in a square yard (commonly needed for carpet, which is often priced per square yard).
This depends on your purpose — for flooring, you typically want to include every area that needs covering, including closets, unless specifically excluded.