How to Measure for Carpet Stair Runners

Measure the stair riser from the bottom of the first stair to the top of the one above it, using a measuring tape. For a stair runner with a waterfall effect, which is stretched straight down from the lip of one stair to the inside point of the next, keep the measuring tape straight and stretch it in the same manner. It will sit at a slight diagonal from the bottom of the riser to the edge of the lip on the stair above. For an upholstered runner, which is fitted to the lip of the stair tread rather than stretched over it, measure straight up the riser from the bottom to the top point where the underside of the lip meets the vertical riser.

Measure the stair depth. This is the horizontal portion of the stair. For a waterfall runner, measure from the back of the step to the edge of the lip. This measurement should end where the riser measurement began. For an upholstered stair runner, place one end of the measuring tape flat against the back of the stair step. Extend the measuring tape across the stair step and over the lip so your measurement ends on the underside of the lip, where it meets the vertical riser.

Count the number of risers and stair steps. Multiply the number of risers by your riser measurement and the number of steps by the stair depth measurement. Add the additional length desired at the top and bottom of the stairs to your total measurement. This gives you the total length needed for your stair runner carpet.

Measure the width of the stairs from one edge of the step to the other. Make a note of this measurement and consider how much of the stair you want your runner to cover. Stair runners are typically 26 inches or 31 inches wide, though custom sizes are available. Subtract the width of the runner from the width of the stair, and divide the remainder by 2 to determine how much of the stair will show on either side of the runner.