What the animation shows
The animation and the step-by-step video above use your numbers. Here is the same walkthrough written out for the default example.
What you enter
- Rectangular rooms or areas: 12 × 15 ft.
- Add an odd-shaped area: L-shape. Set to None if every area is a rectangle. Its size uses dimensions A–D below.
- Shape size A: 20 ft. Triangle: base. Circle or half circle: diameter. Trapezoid: bottom side. L-shape: overall length.
- Shape size B: 16 ft. Triangle: height. Trapezoid: top side (parallel to A). L-shape: overall width. Not used for circles.
- Shape size C: 8 ft. Trapezoid: height between the parallel sides. L-shape: length of the missing corner. Otherwise not used.
- Shape size D: 6 ft. L-shape: width of the missing corner. Otherwise not used.
What happens, step by step
- Each area is drawn to scale from your measurements.
- Every square is one foot by one foot: counting them gives square feet.
- The L-shape is the full 20 × 16 ft box minus the missing corner.
- Add them up: 452 sq ft. Divide by 9 for 50.22 sq yd.
The answer: total area is 452 sq ft.
How it’s calculated
- Rectangle: length × width
- Triangle: base × height ÷ 2
- Circle: π × diameter² ÷ 4; half circle: π × diameter² ÷ 8
- Trapezoid: (bottom side + top side) ÷ 2 × height
- L-shape: overall length × overall width − missing corner length × width
- Square yards = square feet ÷ 9; square meters = square feet × 0.0929
Worked example
A 12 × 15 ft bedroom plus an L-shaped living room 20 × 16 ft with an 8 × 6 ft corner missing.
Inputs
- Rectangular rooms or areas
- 12 × 15 ft
- Add an odd-shaped area
- L-shape
- Shape size A
- 20 ft
- Shape size B
- 16 ft
- Shape size C
- 8 ft
- Shape size D
- 6 ft
- Price per square foot (optional)
- 0 $/sq ft
Results
- Total area
- 452 sq ft
- Rectangular areas
- 180 sq ft
- Odd-shaped area
- 272 sq ft
Assumptions and limits
- Floor plans are flat (no slope correction).
- Closets, alcoves and bays are included only if you add them as their own rows.
- No waste allowance — add it in the material calculator you use next.
- 1 sq ft = 0.09290304 m² exactly.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
How do I calculate square footage of a room?
Multiply the length by the width in feet. A 12 × 15 ft room is 180 sq ft. For measurements in inches, divide each by 12 first: 150 in × 100 in is 12.5 × 8.33 ft, or 104.2 sq ft.
How do I measure an L-shaped room?
Measure the full length and width as if it were a rectangle, then subtract the missing corner. A 20 × 16 ft L with an 8 × 6 ft corner missing is 320 − 48 = 272 sq ft. Splitting it into two rectangles gives the same answer.
How many square feet in a square yard?
Nine. A square yard is 3 ft × 3 ft. A 180 sq ft room is 20 sq yd, which is how carpet is often priced.
What is the area of a round patio?
Use π × diameter² ÷ 4. A 10 ft circle is 78.5 sq ft; a 12 ft circle is 113.1 sq ft.