How many inches or feet wide are the 16 ft. Corrugated Galvanized Steel 29-Gauge Roof Panels?

They are 25.75 inches wide

The 16 ft. Corrugated Galvanized Steel 29-Gauge Roof Panels are 25.75 inches wide, with that said, for siding application we recommend overlapping 1 corrugation giving the Panel 24 in. width coverage and for the roofing application it is recommended you side lap 2 full corrugations giving the panel 21.5 in. coverage.