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How to Measure for Carpets


Whether you are considering installing your carpet yourself or just want to be able to get a realistic idea of price, there are some special considerations when measuring for wall-to-wall broadloom.

What You Will Need


  • a measuring tape or a laser distance measurer
  • a calculator (unless you prefer doing math on your own!)
  • some graph paper and a pencil, if you choose to draw your layout

The Basics


  • The basic method of measuring a space is to measure the width of the room, and then the length of the room, and then multiply the two dimensions to get the square footage of the room. Lay your tape measure against the wall at one end of your room, and then extend it to the opposite wall. Do the same for the other two walls in the opposite direction.
  • One common mistake is to measure simply from wall to wall. Unless your room is entered by a step, all rooms have a doorway leading into them. Some rooms have additional doorways to closets, bathrooms, etc.
  • You must be sure to measure into the middle of the doorway. This will add 2 to 3 inches to your overall measurement, so if you have a doorway at either end of the room, you could be up to 6 inches beyond the exact room dimension.
  • If you are measuring an area that leads to stairs going down (such as a hallway or landing) be sure to measure around the nosing (the ledge at the top of the stairs). Hold your tape measure against the opposite wall (or halfway into a doorway), and wrap it all the way around the nosing until it touches the back (riser) of the stair below. Your carpet will need to be this measurement in order to wrap around the nosing.

Add a Little Extra


Once you have taken your measurements, you should always add a little extra to your requirements. This allows for walls that are not perfectly straight, and gives you a bit of a safety net. When measuring, I typically add about 3 inches to each piece of carpet that I will need.

Carpet Widths


Unfortunately, just calculating the square footage of your room doesn’t tell you how much carpet you will have to buy. Broadloom comes in specific widths usually. Therefore, when you buy a piece of carpet off the roll, you have to buy the length you need, by the width of the roll.

Calculating Carpet for Stairs


Calculating how much carpet you need to cover your stairs is one of the most difficult aspects of planning your carpet installation. The carpet on stairs is rarely installed in one single piece, and the calculations require great attention to detail. Let’s review how to determine how much carpet you will need to buy for your stairs.

Be sure to measure carefully!


Stairs come in different shapes, sizes, and configurations. Here are the different types of stairs typically found in a home:

Box Stair


  • A box stair is straight, has no railing posts, and is closed in on all sides.
  • It is typically approximately 3′ wide.
  • The usual allowance for the tread (the flat part you step on) is 10″, and 8″ for the riser (the back of the stair). Therefore, for every box stair, you require 3′ (or the width of your stair) x 18″ of carpet.

Cap Stair


  • A stair that has one open side with railing posts on it is known as a cap stair.
  • It has the same measurements for the tread and riser as a box stair (combined 18″).
  • You will need approximately 4′ of carpet to cover the width, to allow the carpet to flow through the posts and wrap around the outside of the stair.
  • If your stair is open with a railing on both sides of it (a double cap) you will need approximately 5′ of carpet to cover the width.

Pie Stair/Winder


  • A curved stair is called a pie stair or winder.
  • The general guideline is that you will require 4′ (or the width of the stair) x 30″ of carpet for every pie stair — this allows for some manoeuvring of the carpet by the installer to find the best fit.

Open Stair


  • An open stair (sometimes called a Hollywood stair) is a stair with no backing.
  • Measure your stair to determine the width
  • You will need approximately 20″ of carpet to wrap completely around the stair.



  • A bullnose stair is often found at the bottom of a staircase.
  • It is wider than the rest of the stairs, and is rounded on one or both sides.
  • The tread and riser combined have the same measurements as a box stair (18″).
  • Measure the stair to determine the width — in grand staircases, it could be quite wide.
  • You will require a piece of carpet that is the width of the stair plus a few extra inches to wrap around the outer edge of the tread, by 18″.
  • You will need approximately 20″ of carpet to wrap completely around the stair.

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