Square Footage Calculator

1. Select the shape that matches your area. Use "Rectangle / room" for standard rooms and "Wall" for vertical surfaces. For walls, subtract large openings (windows, doors) only when estimating finish material like paint or wallpaper. For L-shaped rooms, measure each rectangular section separately and add the results.
2. Choose your measurement unit. Switch to "Inches" if you measured in inches. The calculator converts to feet automatically before calculating square footage.
3. Enter your dimensions. For rectangles and rooms, enter length and width. For circles, enter the full diameter (distance across). For triangles, measure the base along the bottom edge and the height straight up from that base.
4. Set quantity if you have multiple identical areas. For example, four walls of the same size can be calculated at once by entering 4.
5. Add a waste factor when ordering material. Use 10% for standard flooring or tile layouts. Use 15% for diagonal patterns, herringbone, or rooms with many cuts. Skip waste (leave at 0%) for pure measurement.
6. Enter a price per square foot to see an estimated material cost. Leave this blank if you only need the area.

Pro tip: For irregular rooms, split the floor into rectangles. Measure each rectangle, run this square footage calculator for each section, then add the totals. Label each calculation (kitchen main area, kitchen nook) so you can trace back if the numbers don't match your tape measure.

A standard bedroom runs 10 ft × 12 ft (120 sq ft). A two-car garage is typically 20 ft × 20 ft (400 sq ft). Use these as a sanity check. If your square footage calculator result is much higher or lower than expected, double-check whether you entered feet or inches.

For contractor takeoffs, compare the base area to the waste-adjusted total. The calculator shows both numbers when you add a waste factor, so you can quote measured area to the client and order the higher quantity from the supplier.

Square footage is a measurement of two-dimensional area in square feet. This square footage calculator uses the standard geometry formula for each shape and converts your inputs to feet before calculating. One square foot equals a 1 ft × 1 ft area (144 square inches).

Rectangle, room, or wall

Square feet = Length (ft) × Width (ft)

For walls, use length × height instead of length × width. A 14 ft long wall that is 8 ft high has 112 sq ft of surface area.

Circle

Square feet = π × Radius²

The radius is half the diameter. If you measured across the full circle (diameter), divide by 2 first. A 10 ft diameter circle has a radius of 5 ft, so the area is 3.1416 × 25 = 78.54 sq ft.

Triangle

Square feet = Base × Height / 2

Height is measured perpendicular to the base, straight up from the bottom edge. A 12 ft base with an 8 ft height gives 48 sq ft.

Trapezoid

Square feet = (Base 1 + Base 2) / 2 × Height

Base 1 and Base 2 are the two parallel sides. Height is the perpendicular distance between them.

Converting from inches

Divide each inch measurement by 12 to get feet before multiplying. Entering 144 inches as 144 feet is the most common measurement error. This calculator lets you switch to "Inches" mode so the conversion happens automatically.

Worked example

Given a 12 ft × 10 ft room with 10% waste for flooring:

• Base area = 12 × 10 = 120 sq ft
• Waste = 120 × 0.10 = 12 sq ft
• Total to order = 120 + 12 = 132 sq ft
• Square yards = 132 / 9 = 14.67 sq yd
• Square meters = 132 × 0.0929 = 12.26 sq m

Assumptions

This calculator measures flat, two-dimensional area. It does not account for sloped surfaces, vaulted ceilings, or three-dimensional volume. For rooms with closets or alcoves, measure each rectangular section and add them. Subtract window and door openings only when estimating finish material (paint, wallpaper) that won't cover those areas.