Use the exact section unit weight
Take pounds per foot from the applicable section table, mill data, or project material list.
Do not substitute a visually similar beam because section weights can differ substantially.
Multiply by actual cut length
Weight for one member equals published unit weight times member length.
Use the takeoff or fabrication length appropriate to the purpose of the estimate.
Multiply by piece count
Group identical marks only when section and length are truly the same.
Keeping marks separate makes the total easier to reconcile with drawings and procurement.
Add fabricated components separately
End plates, stiffeners, base plates, connections, bolts, decking, and other steel are not included in a bare beam's pounds-per-foot value.
Coatings and fireproofing also require separate quantity methods.
Do not confuse weight with design
A weight takeoff cannot establish member capacity, deflection, stability, connections, or code compliance.
Use structural documents and qualified design for member selection.