Q&A for How to Calculate Carpet on Stairs

A square foot is the area of a square one foot (12 inches) on a side, so there are 144 square inches in a square foot. So divide the number of square inches by 144 to get square feet. Or if you're lazy, just type something like "5000 square inches in square feet" into a Google search, and Google won't just tell you the answer, it will bring up a conversion calculator!

You don't. 1887 sq inches should be divided by 144 sq inches (the amount of sq inches in a sq foot), and you should get 13.1 or so sq feet.

Round up, then just cut off the extra carpet.

You typically should not have to seam carpet for stairs. If for some reason you do, you should lay the pieces of carpeting out on a flat surface big enough to accommodate the whole set of stairs flat, make sure the looping of the carpet is going the same way. Seam your carpet as normal, then cut the carpet to the measurments of the stairs. Transfer to the stairs. Install as normal.