How To Calculate Rebar Lengths

Rebar, short for reinforcing bar, is a steel bar used to reinforce concrete and masonry structures. When dry and compressed, concrete may crack or break under tension without rebar. Rebar has steel ridges that attach to the concrete and help strengthen the concrete. Construction crew chiefs and project managers must calculate length, total weight and other parameters to support rebar cost estimates, billing and supply concerns as well as installation concerns. In fact, the total weight of rebar material is the end result relative to cost and the rebar length associated with each slab of concrete feed final weight calculations.

Step 1

Measure the entire length of the concrete slab. This is your slab length, or "SL." As an example, assume your SL is 50 feet.

Step 2

Calculate rebar length for the slab — "RL" — using the formula: RL = SL – 0.5 units. The 0.5 allows for sufficient clearance for fitting the rebar within the slab. The term "units" refers to the same units as the slab length. For example, if SL is 50 feet, RL = 50 feet – 0.5 feet = 49.5 feet.

Step 3

Repeat Step 1 and Step 2 for each slab to determine the RL associated with each slab. You will need 1 stick of rebar for every 8 inches of slab width.