Having clean and nice carpets is the best way to welcome a guest. Thus, it is important that you keep those extra flaps of carpet fabric well hidden under the furniture and tucked underneath. But to avoid going the extra effort to tuck under the carpet and hide it under furniture, you should know how to measure carpets perfectly. Knowing so would let you have a perfectly sized carpet for your floors, stairs and entryways that gives a warmer welcome than carpets with unruly flaps.
Aside from getting the best looking floors as possible, knowing how to measure carpets would also give you a lot of savings. Most carpet installation companies will not provide you with measuring services thus they may charge you for a carpet that are a few inches too wide or too long for your floor. Also, knowing how long or wide of a carpet you need would help keep you away from scams. Knowing the right dimensions of a room would allow you to punch in a specific order without any extra services they may offer.
First thing to do when measuring a carpet is to make a sketch of the area you want carpeted. You don't need to be artistic with the blueprint. Just use a pencil and a ruler to make the lines straight. Having a blueprint would allow you to put measurements on every possible side on the area including the sides of a closet, stairs, and hallways. Use a 25'-30' tape measure and measure the longest and widest part of the room. While jotting down the measurements though always make sure that you write it in feet-cm. Like for example, instead of writing 147", write down 12'-3". That would surely make the installation a lot faster since the salesperson you talk to will not have to convert the measurements to feet.
While measuring from wall to wall, keep in mind that the installation guy will put the carpet seams on where your door closes. So ideally the measurements would be short of about 6 inches on walls having doors. So to make things simple, try to measure the space between two doorways.
If there are short measurements on a room, you should also add a couple of inches at each seam. This is because installers will cut a seam edge from every side so that you will have a straight carpet edge. This is important since you don't want your carpet seams to show up on each side. A straight edge will keep the seams invisible. As the installers cut the seam edges, you will supposedly lose a few inches so to ensure that they have enough carpet edges to cut through while still having a perfectly sized carpet, add a few inches of measurement.
Now, how to measure carpets for supposedly square rooms? You should still proceed to measure every side. Not all sides of the room will have the same length. And even square rooms will have different measurements for each side, which could differ from a few centimetres to a whole ft.