Channel is specified by a size and weight per foot. There are various weights for each size of channel. You could measure the cross sectional area of the channel x length x .2833 to get the total weight.

Have a nice day

Gerald Austin

Besides the rolled channel shapes that Gerald refers to, there are also channels that are manufactured out of sheet or plate material. These shapes usually have a radius on the heel of the channel and are a uniform thickness throughout.
If what you have is a hot rolled shape, my Ryerson book shows two weights for a 5" channel, one at 6.7 lbs per foot and the other at 9.0 lbs per foot. Also be aware there are MC channels or sometimes called ship channels that have different weights and dimensions. Luckily they do not come in a 5" size. Hope this helps.

The Engineers Edge website has a lot of useful tables and data on a number of engineering subjects. This page leads you to tables for various structural steel shapes:
http://www.engineersedge.com/structural_shapes_menu.shtml
Cross sectional areas are given in the tables for each standard size of structural steel shape.

Any engineering manual has lot of tables showing the weights of all kinds of structural steel.
Giovanni S. Crisi
Sao Paulo - Brazil