To calculate the square footage of a room, multiply its length by its width in feet. A room 15 feet long and 12 feet wide is 15 × 12 = 180 square feet. For a whole house, work out every room the same way and add them together. Split awkward shapes into rectangles first.
The free square footage calculator does the adding for you, accepts feet and inches as you would write them, and gives the total in square feet and square metres, plus the price per square foot.
What do you need to measure square footage?
A tape measure or laser measure, a notepad or phone, and ten minutes per floor. A laser measure is faster and more accurate for long rooms, and easier to use alone.
Measure each room wall to wall at floor level, in the longest and widest directions. Write down the room name and both measurements before moving on. If the walls are not quite square, measure both ends and use the average.
How do you measure a room in feet and inches?
Most tape measures show feet and inches, so a wall might be 12 feet 6 inches. To multiply, convert the inches to a fraction of a foot by dividing by 12: 6 inches is 0.5 feet, so the wall is 12.5 feet.
| Inches | Feet |
|---|---|
| 1 | 0.083 |
| 3 | 0.25 |
| 6 | 0.5 |
| 9 | 0.75 |
| 11 | 0.917 |
In the calculator you can skip the conversion and type 12' 6", 12ft 6in or just 12 6.
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How do you calculate an L-shaped room?
Split it into two rectangles that do not overlap. Work out each one and add them. A kitchen-diner might be a 14 × 10 foot main area (140 sq ft) plus a 6 × 5 foot dining nook (30 sq ft), so 170 square feet in total.
The same approach works for any room made of straight walls: divide it into rectangles and triangles, then add them up.
How do you handle other shapes?
| Shape | Formula | Example |
|---|---|---|
| Rectangle | Length × width | 15 × 12 = 180 sq ft |
| L-shape | Rectangle A + rectangle B | 140 + 30 = 170 sq ft |
| Triangle | Base × height ÷ 2 | 8 × 6 ÷ 2 = 24 sq ft |
| Circle or round bay | π × (diameter ÷ 2)² | 6 ft bay: 3.14 × 9 = 28.3 sq ft; half of that for a half-round bay |
| Known area | Use it as given | From a plan or survey |
How do you calculate the square footage of a whole house?
Add up every finished room and the circulation between them: halls, landings and stairs on each floor. Then decide what to leave out. Whether garages, unfinished basements, loft space with low ceilings, conservatories or outbuildings count depends on the measurement standard you follow, so be consistent and say what is included.
- In the US, ANSI Z765 is the common standard for single-family homes. It counts finished, above-grade space, measured to the outside of exterior walls, and excludes areas with ceilings lower than its minimum height. Appraisers and many MLS boards follow it.
- In the UK, floor areas are normally quoted as gross internal area, measured to the inside of the external walls, under the RICS professional standards. Energy Performance Certificates also show a total floor area, measured on their own basis.
If a number will appear in a listing, valuation or lease, use the standard your market expects and, ideally, a professional measurement.
How do you convert square feet to square metres?
Divide square feet by 10.764. Multiply square metres by 10.764 to go the other way. So 1,000 sq ft is 92.9 m², and 100 m² is 1,076 sq ft. The calculator shows both, which helps when one portal displays square feet and another square metres.
What is price per square foot and how do you work it out?
Divide the price by the floor area. A £450,000 flat of 900 sq ft is £500 per square foot. Agents use it to compare homes of different sizes on a level footing and to sense-check a valuation against recent sales. Enter an asking price in the calculator and it works out both price per square foot and per square metre.
Price per square foot is only meaningful when the areas being compared were measured the same way. A listing that includes a garage will look cheaper per square foot than one that does not.
What if you only have a floor plan?
Use the floor plan ruler. Set the scale from one dimension you know, then trace each room to get its area. It works with PDF and image plans. There is a step-by-step guide in how to measure a floor plan to scale.
Common mistakes to avoid
- Mixing units. Measuring some rooms in metres and others in feet.
- Measuring skirting to skirting in one room and wall to wall in another. Pick one and stick to it.
- Counting overlaps twice. When splitting an L-shape, make sure the rectangles do not overlap.
- Forgetting halls and landings. They add up across a house.
- Rounding too early. Keep two decimal places until the final total.
Once you know the floor area, show buyers what the space can do. An empty room is hard to judge from its size alone; virtual staging shows how furniture fits, and a floor plan in a 360° tour helps buyers understand the layout.
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