Room Size Calculator
Use this free room size calculator to find the square footage, perimeter, and volume of any room. Works for simple rectangular rooms and L-shaped rooms, with automatic conversions to square meters and square yards.
How to Use the Room Size Calculator
- Measure length and width: Use a tape measure or laser measure along each wall, in feet.
- Add ceiling height (optional): Include this if you need room volume, for example to size an air conditioner or dehumidifier.
- L-shaped room? Check the box and enter a second rectangular section — the calculator adds both areas together.
- Read your results: Get square footage, perimeter, volume, and conversions to square meters and square yards instantly.
What Is This Room Size Calculator?
This room size calculator (also called a square footage calculator) finds the floor area, perimeter, and volume of a room from simple length and width measurements. It handles both rectangular rooms and L-shaped rooms.
Why Use a Room Size Calculator?
Square footage is the starting point for almost every home project — flooring, paint, tile, furniture layout, real estate listings, and HVAC sizing all depend on an accurate area. Doing the math by hand is easy for a simple rectangle but gets error-prone for L-shaped rooms or when you also need metric conversions.
How Does This Calculator Work?
For a rectangular room, area is length times width, and perimeter is twice the sum of length and width:
Area = Length × Width | Perimeter = 2 × (Length + Width)
For an L-shaped room, the calculator splits the space into two rectangles, finds each area, and adds them together. Perimeter is not shown for L-shaped rooms since it depends on exactly how the two sections join, which a simple two-rectangle model can't determine reliably.
Worked Example: L-Shaped Room
A living room measures 12 by 10 feet, with an alcove section measuring 6 by 4 feet attached to it:
- Main section: 12 × 10 = 120 sq ft
- Alcove section: 6 × 4 = 24 sq ft
- Total area: 120 + 24 = 144 sq ft
- In square meters: 144 × 0.092903 ≈ 13.38 m²
Load this example in the calculator above.
Room Size Calculator FAQs
Measure the room's length and width in feet, then multiply them together. A room that is 12 feet by 10 feet has 120 square feet of floor area. For L-shaped rooms, split the room into two rectangles, find each area, and add them together.
Divide the room into two rectangular sections along a straight line, measure the length and width of each section, calculate each area separately, then add the two areas together. This calculator has a built-in second-section field for exactly this case.
Multiply the square footage by 0.092903 to get square meters. For example, 120 square feet equals about 11.15 square meters. This calculator converts automatically.
Multiply the floor area (length × width) by the ceiling height to get the volume in cubic feet. Room volume is useful for sizing air conditioners, heaters, and dehumidifiers, which are often rated by the cubic feet of space they can handle.
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