Tap & Trowel Home-project calculators & repair guides

Square footage calculator

Add each room or section as a rectangle, circle or triangle. Tick “subtract” for anything you're leaving out, such as a kitchen island. The total updates as you type. The defaults are an L-shaped room split into two rectangles.

By Jordan Hale · Updated

Units

Measurements in decimal feet. 6 inches = 0.5 ft and 3 inches = 0.25 ft.

  1. Area 1
  2. Area 2
Leave at 0 for the room size. Add 5–15% when ordering flooring.
Optional: estimate the cost

Total area

Square feet
–
Square meters
–
Square yards
–
Acres
–
Cost
–

Net of any subtracted areas, plus your extra allowance.

Illustration of an L-shaped room outline divided into two rectangles by a dashed line, with a tape measure along one wall and a notepad and pencil beside it.
Illustration

How the calculator works

  • Rectangle: length × width.
  • Circle: π × (diameter ÷ 2)². People can measure a diameter with a tape; a radius is harder to find.
  • Triangle: base × height ÷ 2. The height is measured square (at 90°) to the base, not along the sloping side.

Each area is added, or subtracted if ticked. The net total can't go below zero, and then your extra allowance is applied. Square yards are ft² ÷ 9. An acre is 43,560 ft². A square foot is exactly 0.09290304 m².

Worked example: an L-shaped room

Split an L into two rectangles that don't overlap: a 12 × 15 ft main room and an 8 × 6 ft alcove.

  • 12 × 15 = 180 ft²
  • 8 × 6 = 48 ft²
  • Total = 228 ft² (21.2 m², 25.3 yd²)

Ordering laminate for it with 10% for cuts? Set the allowance to 10 and you get 250.8 ft². Then round up to whole cartons using the coverage printed on the box.

Measuring tips that change the answer

  • Measure at floor level, wall to wall, and in two places for long rooms. Walls are rarely perfectly straight.
  • Convert inches carefully. 12 ft 9 in is 12.75 ft, not 12.9 ft.
  • For a whole house, “square footage” on a listing or appraisal follows specific rules. For example, ANSI Z765 measures from the exterior and treats below-grade space separately. A room-by-room total is the right number for buying materials, not for a listing. The measuring guide explains the difference.

Sources

How this page was made. Jordan Hale is the author and is responsible for this page. An AI assistant helped write the code, gather manufacturer data and draft the explanation. The math is covered by automated tests against the published reference values cited below. The calculator gives a planning estimate. It does not replace the product label, your supplier or an engineer. The illustration on this page is AI-generated and shows the general idea, not exact construction details.