Square Footage Calculator

Please enter values greater than 0.
–square feet
–square yards
–square meters
–acres

How to use this calculator

Choose a shape and unit, enter the measurements and press Calculate. The result is shown in square feet, square yards, square meters and acres.

The formula

Rectangle: length × width
Triangle: base × height ÷ 2
Circle: π × radius × radius

Example: A 12 ft × 15 ft room is 180 square feet, which is 20 square yards or 16.72 square meters.

What your square footage result means for your project

The square footage you get is the flat floor area of the shape you measured. It is the number most flooring, carpet, tile and sod suppliers price by. It is not the same as wall area, so do not use it alone to buy paint or drywall.

Measure carefully

Small errors add up. Measuring each side 6 inches too long on a 12 ft by 15 ft room changes the area by about 14 square feet. A few habits help:

  • Measure wall to wall at floor level, not along the baseboard top.
  • Round up to the nearest inch. You can enter inches directly and let the tool convert.
  • Measure twice in different spots. Older rooms are often not perfectly square.
  • For closets and bay windows, measure each one as its own shape.

Working with odd shapes

Most spaces break into rectangles, triangles and circles. A triangular garden corner with a 12 ft base and 8 ft height is 48 square feet (12 × 8 ÷ 2). A round patio 10 ft across has a 5 ft radius, so it covers about 78.5 square feet (3.1416 × 5 × 5). Add the pieces together for the total. Subtract any area you will not cover, such as a kitchen island or a fireplace hearth.

Turning area into a shopping list

Once you know the area, add a waste allowance before you buy. Cuts, mistakes and pattern matching use up material.

  • Flooring and tile: add about 10 percent, or 15 percent for diagonal layouts.
  • Sod and turf: add about 5 percent for trimming around edges.
  • Carpet: it is sold off rolls of fixed width, so seams may add more.

For example, the 180 square foot room from the formula above needs about 198 square feet of flooring with 10 percent extra. If the product costs $3 per square foot, plan on about $594 for material before tax and underlayment.

Common mistakes

  • Mixing units, such as length in feet and width in inches.
  • Using the listed home size for one room. Listed square footage usually includes walls and hallways.
  • Forgetting the waste allowance and coming up one box short.
  • Rounding down measurements to keep the number small.

If you are pricing a sale or a rental, note that official home size rules vary by area and appraiser. For buying materials, your own careful room measurements are what count.

Frequently asked questions

How do I calculate square footage of a room?
Multiply the length by the width, both in feet. A 12 ft by 15 ft room is 180 square feet.
How do I calculate square footage of an L-shaped room?
Split it into two rectangles, calculate each area, then add them together.
How many square feet are in a square yard?
One square yard is 9 square feet.
How do I convert square feet to square meters?
Multiply square feet by 0.0929.
How many square feet are in an acre?
One acre is 43,560 square feet.
How do I calculate square footage of a whole house?
Measure each room and hallway separately, find each area, then add them up. Include finished living space and skip garages, unfinished basements and open porches. Appraisers usually measure the outside walls instead, so your room-by-room total will often come out a little lower than the listed home size.
How do I find the square footage of walls for painting?
Multiply the room perimeter by the wall height. A 12 ft by 15 ft room has a 54 ft perimeter, so 8 ft walls give 432 square feet. Subtract about 20 square feet per door and 15 square feet per window. Then check the paint can for its coverage per gallon.
Is square footage the same as linear feet?
No. Square feet measure area, such as a floor. Linear feet measure length only, such as baseboard, fencing or trim. A 12 ft by 15 ft room has 180 square feet of floor but needs about 54 linear feet of baseboard, minus the width of any doorways.