Rebar Lapping Length

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Equation / Last modified by AndrewBudd on 2018/12/12 20:25
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The Rebar Lapping Length calculator computes the length overlap needed at rebar joints based on the size of the rebar (rS) and the lapping factor (LF).Rebar Lapping.png

INSTRUCTIONS - Enter the following:

  • (rS) The size of rebar  which is used to compute the diameter for lapping considerations.
  • (LF)  The lapping factor is the multiple of the diameter of the rebar to specify the lapping distance.  40 (default) and 60 are common.

Lapping Length: The calculator returns the length of rebar lap in inches.   However, this can be automatically converted into other length units (e.g. centimeters) via the pull-down menu.  
Rebar Calculators:BNT-40_2016-768x768.jpg     BNT-40 Automatic Rebar Tier

  • To compute the Weight of Rabar in a slab, CLICK HERE.
  • To compute the Surface Area of a slab, CLICK HERE.
  • To compute the Surface Area of Concrete Forms, CLICK HERE.
  • To compute the Volume of Concrete in a slab, CLICK HERE.
  • To compute the Weight of Concrete in a slab or wall, CLICK HERE.


When the dimensions of your slab or wall exceed the length of a single piece of rebar, it is required to lap the rebar and tie the bars them to create the added length.  There are a few considerations.  First, the length of the lap is often specified as 40 times the diameter of the rebar.  In this case, 40 is lapping factor.  60 is also a common factor, but the engineering specifications should always be applied.  See these YouTube videos to better understand rebar lap:

Second, the typical length of rebar is 40' and 60' in the United States.

See how much the rebar will weigh - Rebar Weight