How to Calculate Square Footage: Step-by-Step Guide

What Is Square Footage?

Square footage is the area of a two-dimensional space measured in square feet. One square foot is a square that is 1 foot wide and 1 foot long. Square footage is used for flooring estimates, real estate listings, paint calculations, landscaping, and HVAC sizing.

How to Calculate Square Footage of a Rectangle

The formula is simple: Area = Length × Width

1. Measure the length of the room in feet.
2. Measure the width of the room in feet.
3. Multiply the two numbers together.

Example: A bedroom that is 12 feet long and 10 feet wide = 12 × 10 = 120 square feet.

If your measurements are in inches, convert to feet first by dividing by 12 (so 144 inches = 12 feet). If in meters, multiply by 10.764 to get square feet.

Calculating Square Footage of an L-Shaped Room

For an L-shaped room, divide it into two rectangles, calculate each separately, then add them together.

1. Identify where you can split the L-shape into two rectangles.
2. Measure and calculate Rectangle A (e.g., 10 × 8 = 80 sq ft).
3. Measure and calculate Rectangle B (e.g., 6 × 5 = 30 sq ft).
4. Add: 80 + 30 = 110 square feet.

Square Footage of a Triangle

Formula: Area = (Base × Height) ÷ 2
Example: A triangular corner with a base of 8 feet and height of 6 feet = (8 × 6) ÷ 2 = 24 square feet.

Square Footage of a Circle

Formula: Area = π × radius²
Example: A circular patio with a diameter of 14 feet. Radius = 7. Area = 3.14159 × 49 ≈ 153.9 square feet.

Converting Measurements

To Convert From	To Square Feet	Multiply By
Square inches	Square feet	÷ 144
Square yards	Square feet	× 9
Square meters	Square feet	× 10.764
Acres	Square feet	× 43,560

Square Footage for Flooring Projects

When buying flooring, always add 10–15% extra for waste, cuts, and mistakes. So for a 200 sq ft room, buy materials for 220–230 sq ft. For diagonal tile or complex patterns, add 15–20%.

Measuring Oddly Shaped Rooms

For rooms with alcoves, bays, or cutouts: measure the full outer rectangle first, then subtract any sections that are not part of the room. Alternatively, sketch the floor plan on paper, divide it into simple shapes, and add all the areas together.