When you want to install walltowall carpet, you can get an idea of how much carpet you'll need by taking a few simple measurements and doing a little math. Carpet is sold in square yards, the equivalent of 9 square feet. It usually comes in 12footwide rolls and each piece must be laid in the same direction. That means you may have to buy more than your calculations show, to limit the number of seams. Use your basic calculation as an estimate for budgeting purposes. Confirm the actual amount with a carpet installer or retailer before your order your carpet.
Things You'll Need
 Tape Measure
 Calculator

Measure the length of your room, from the farthest points. For instance, if your room has a carpeted closet, measure to the back wall of the closet. Measure the width of the room in the same way. If your room is Lshaped, break it into two rectangles and measure the length and width of each one.

Multiply the length of the room by its width to calculate its square footage. For example, a 12by12foot room is 144 square feet. If you have an Lshaped room, calculate each section's square footage, then add them together to get the total square footage.

Divide the room's square footage by 9. This gives you the number of square yards of carpeting needed to cover the room.
Tips & Warnings
 Remember to always measure from the furthest point of any room to the furthest opposite wall. Closets and dormers should be included for a seamless carpet. If this is new to you, the easiest way to purchase carpet is to inform the salesman of the measurement (length x width) of the room. Let him do the math, you can always check his calculations with your own!
 If you plan to lay the carpet yourself, make sure that you have calculated the correct area and the right amount of carpet needed to minimize seams. Most stores will not give you a refund if you've made a mistake.
References
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