Measure the room. The first thing you need to do is determine its length and width of the room you want to carpet. These numbers are very important, because they will determine how much carpet you end up buying and its overall price. You determine the area of the room by multiplying the length times the width. The formula is A= l x w. Remember that you will always need to round the numbers up. For example, if you have one wall that is 14.2 feet wide and another that is 19.4 feet long, you will want to round up to 15 feet and 20 feet for your calculations. That is the minimum amount of carpet you will need, but always buy extra. Remember, measure in feet and inches, not in meters.
Measure the room again! It is easy to make a mistake when measuring. And when you multiply and do other math, it is easy to make additional errors. So always measure at least twice. In fact, it's not a bad idea to measure three times. If your numbers are off, you can make a huge mistake by not purchasing enough carpet. So always make sure to measure correctly, and then buy several feet of extra carpet, just in case you measured incorrectly or make a mistake later in the process.
Price carpet per foot. Pricing carpet per foot is as easy as doing a little research. Just go to a carpet store, patronize an online carpet retailer or browse a carpet catalog. Once you find the carpets you like, you need to write down the price per foot, so you can calculate the total cost of the carpet.
Now that you have the area of the room and the price per foot of the carpet, it's time to pull out your calculator and find the total cost. Simply multiply the area of the room times the price per foot. For example, if the area of the room is 188 square feet and the price per foot of carpet is $7.99, the total is $1502.12.
Calculate sales tax. Once you find the total cost of the carpet, you will still need to add in sales tax. Take the percentage your state charges and multiply it by the cost of carpet. For example, if the sales tax where you live is 7percent, then you will calculate the cost this way: $1502.12 (cost of carpet) x .07 (sales tax) = $105.15. The sales tax is $105.15 and must be added to the $1502.12 for your total cost, which comes to $1607.27.