Carpet: add a waste buffer before you buy
Carpet is often priced by the square yard. Measure the room in ft² first, divide by 9, and then add roughly 10% for cuts, seams, and trim waste.
Example: a 12 × 15 ft bedroom is 180 ft². That converts to 20 yd², and a 10% buffer brings the shopping target to about 22 yd².