Take the length times the width, divide by nine, and you have your square yards. That number is enough to price shop with. It is not enough to order carpet, and the gap between the two is where most surprises live.
Here is how to measure so the number you carry into a store is a number a store can actually use.
Start with the basics
Measure at the widest point of the room, wall to wall, and measure in inches rather than feet. Inches are easier to be accurate with and nobody has to guess what “about twelve and a half feet” means.
Do it in two places. Rooms in older Pittsburgh houses are rarely square, and a room that is 143 inches at the door and 147 inches at the back wall needs to be treated as 147.
Write it down as width by length. Then convert:
- Square feet = length in feet times width in feet
- Square yards = square feet divided by nine
A 12 by 12 bedroom is 144 square feet, or 16 square yards. A 15 by 15 living room is 225 square feet, or 25 square yards.
Now add the parts people forget
Closets. Measure them separately and add them. A reach-in closet is small, but it needs its own piece cut from the same roll so the color matches, and that piece has to come out of the same purchase.
Doorways and thresholds. Carpet runs a few inches into the doorway so the transition strip has something to hold. Add about four inches at every doorway.
Bay windows, alcoves, hearths. Any bump-out in the wall is extra length, and any bump-in (a fireplace hearth, a built-in) does not reduce the yardage as much as you would hope, because the carpet is still cut from a full width.
Irregular shapes. Break an L-shaped room into two rectangles, measure each, and add them.
The twelve foot rule, which explains everything
Carpet is manufactured in rolls twelve feet wide, and you buy a length off that roll rather than an area of carpet. So a room 11 feet wide by 14 feet long means buying a piece 12 by 14: you pay for 168 square feet to cover 154, and the extra foot of width becomes offcut.
Any room wider than twelve feet needs a fill piece, and that changes the number more than most people expect. The full explanation, including what the fill costs you and why it cannot be cut sideways, is in how wide does carpet come.
Seams, and where you want them
Any room wider than the roll gets a seam. The question is where.
Good seam placement runs the seam parallel to the main light source, away from the middle of the room, and never across a doorway or a traffic path. A seam in the walkway between a couch and a doorway will show within a year.
This is the single biggest reason to have someone measure before you order. A layout that saves two yards of material but puts the seam in a bad spot is a false economy, and it is the kind of judgment call that comes from having installed a few thousand rooms.
Measuring stairs
Stairs are counted, not squared.
Count your steps. A standard flight in a Pittsburgh row house is 13 or 14. Then measure one step: the tread depth (front to back of the flat part), the riser height (the vertical face), and the width.
For a box stair being wrapped, each step uses roughly the tread depth plus the riser height plus about three inches for the nosing overhang. That is commonly 18 to 20 inches of carpet length per step.
So 13 steps at 19 inches each is about 247 inches of length, or a bit over 20 feet, at the stair width.
Landings and winders (the pie-shaped steps on a turn) are measured individually and use more material than a straight step. Count them separately when you call.
If you have bare wooden steps and are adding risers, add them before the carpet goes down. We had a customer this summer who finished his basement, had bare wooden steps, and was smart enough to ask about risers first. Carpet over a finished riser looks right. Carpet over a gap does not.
What about padding and tack strip
Padding is bought for the same square yardage as the carpet and comes in six foot widths, so it seams differently and does not have the same offcut problem.
Tack strip is sold by the linear foot around the room perimeter. For a 12 by 15 room that is 54 feet, minus doorways.
You do not need to calculate these yourself. Just know they are line items and ask whether a quote includes them.
A shortcut worth knowing
If your room is under about twelve by twenty, measure it and then go look at the remnant wall before you look at rolls. A remnant is already a twelve foot wide piece of a set length, so the question becomes simple: is this piece long enough for my room, yes or no.
Bring your measurements. That is genuinely all you need to answer it in about ten seconds.
When you are ready for a real measure
Call (412) 885-1444 with your numbers and we can give you a ballpark over the phone. When you are ready to order, we come out and measure properly. There is a charge for the in-home measure and it gets credited back to you when you purchase.
The person who measures is the person who installs, so the layout that gets planned at your house is the layout that gets cut.
