Rebar Weight
Total weight for a run of US bar sizes #3–#8.
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The engineering
US bar numbers are eighths of an inch of nominal diameter — a #4 is 4/8 = 1/2 in — and the unit weights on this card (0.376 to 2.67 lb/ft for #3–#8) are the ASTM A615 nominal values, computed from the nominal diameter at steel's 490 lb/ft³. Deformation ribs are already accounted for: the nominal diameter is defined so the bar weighs as a plain round of that size.
Weight is how rebar is bought and how delivery tickets are checked, so this card is takeoff arithmetic. It does not include lap splices, hooks, or chairs — a real takeoff adds laps (commonly 40 bar diameters or more, per the drawings), which can add 10–15% to the straight-run total.
Where this math comes from
Ernest Ransome patented the twisted square bar in 1884 so concrete could grip the steel, and the deformed round bar with rolled ribs followed as mills learned to hot-roll patterns. What made rebar a commodity was paperwork: ASTM A15, issued in 1911, standardized billet-steel reinforcing bars, and the numbered eighth-inch size system let a Chicago detailer and a Texas mill mean the same thing by '#5'.
Today's A615 nominal weights are the same arithmetic every estimator has used for a century — diameter squared, times steel density, priced by the ton and checked at the scale house.
- 1867Joseph MonierReinforced concrete patented — steel goes into the pour.
- 1884Ernest RansomeTwisted rebar patent — mechanical bond by geometry.
- 1911ASTMA15 standardizes reinforcing bars; the numbered size system follows.
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