Select one stair tread and measure its depth and the step height. Multiply the height by the number of step and the depth by the number of treads. Add the two figures together then add 6 inches to account for waste. This is the total length of runner you will need. If you need more than one runner, add an additional 12 inches to the total to account for the seams where the carpets will join.
Install Carpet Runner
Cut a strip of double-sided tape slightly shorter than the width of the rug and press the tape along the top edge of the riser of the first tread, placing it just under the nose.
Line up the top edge of the runner rug with the tape and press firmly. Use the carpet tacks to hold the rug in place, starting in the center and then at every three inches on either side. Be sure there is a nail in each of the outer edges.
Smooth the rug against the stair. Nail the rug to the bottom of the stair in the center of the rug and then at every three inches on either side.
Repeat the process of nailing the runner to the base of the riser as above, then continue over successive treads until you reach the last tread you can cover.
If need a second runner
If you are adding a second runner, after you have stapled to the bottom of the last finished riser, trim the trailing edge of the first runner, leaving a 2-inch piece free to overlap.
Overlap with the second runner, carefully aligning the sides of the two runners and pressing the finished edge against the riser.
Staple into the second runner as above, then continue the installation process as described above for the remaining treads to be covered
Finish the step
Fold the end of the runner under and press it tightly against the final riser to create a hem. Nail into place against the riser. If the final riser ends in a moulding, fold and staple the hem so that it sits above that piece.