Square Footage Calculator

How to measure a room

Measure wall to wall at floor level along the longest length and the widest width, and write down feet and inches. Convert inches to a decimal of a foot by dividing by 12: 10 feet 6 inches is 10.5 feet, and 11 feet 3 inches is 11.25 feet. Multiplying 10 ft 6 in by 11 ft 3 in as "10.6 × 11.3" is a common mistake that overstates the area.

For an L-shaped or irregular room, split the floor into rectangles that do not overlap, measure each one, and add them up. Choose "Several rectangles" above and enter up to four. A closet or bay can be its own rectangle.

Circles and triangles

A circle's area is π × radius², where the radius is half the diameter. A round patio 10 feet across has a radius of 5 feet and an area of π × 25 = 78.54 square feet.

A triangle is half of a rectangle: base × height ÷ 2. The height must be measured square to the base, not along the sloping side. Triangles are useful for gable walls, angled garden beds and the odd corners of a lot.

Square feet, square yards and square meters

One square yard is 3 ft × 3 ft, or 9 square feet, so divide square feet by 9 to get square yards; carpet and some sod are still priced that way. One foot is exactly 0.3048 meters, so one square foot is 0.09290304 square meters.

The figure here is the floor area of the space. Listing or appraisal square footage for a home follows its own rules about what counts (for example, how stairs, garages and below-grade space are treated), so it can differ from a room-by-room total.

The formulas

• A = area in square feet
• L, W = length and width in feet
• d = diameter in feet
• b, h = triangle base and perpendicular height in feet

Example: an L-shaped room

1. Split the room into two rectangles: 12 × 15 ft and 10 × 8 ft.
2. Areas: 12 × 15 = 180 sq ft and 10 × 8 = 80 sq ft.
3. Total: 180 + 80 = 260 sq ft.
4. In square yards: 260 ÷ 9 = 28.89 sq yd. In square meters: 260 × 0.09290304 = 24.15 sq m.
5. At $4.50 per sq ft for flooring, the material for the exact area costs 260 × 4.50 = $1,170 before any waste allowance.

Frequently asked questions