# Rebar Grid Weight with Lapping Factors

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The Rebar Grid Weight with Lapping Factors calculator computes the total weight of rebar in one or more mats of rebar in a concrete slab including lapping.

INSTRUCTIONS: Choose your preferred units and enter the following:

• (L) The length of the slab
• (W) The width of the slab
• (oC) The on-center spacing of the rebar spacing (defaults 18")
• (i) The inset distance from the side of the slab to the rebar grid (default of 3").
• (m) The number of mats.  (default is one).
• (rS) The size of rebar  which is used to compute the diameter for lapping considerations.
• (rL) The length of the pre-cut reinforcement bars being used to determine if lapping is required.
• (LF)  The lapping factor is the multiple of the diameter of the rebar to specify the lapping distance.  40 (default) and 60 are common.

Weight of Rebar: The calculator returns the weight of rebar in pounds.   However, this can be automatically converted into other weight units (e.g. kilograms or tons) via the pull-down menu.  Tocompute the length of reinforcement bars, use the Rebar LENGTH Calculator.

### General Information

The user inputs are as follows:                   Rebar Grid (one mat) with no lapping

• The slab is defined by a length (l) and a width (w).
• The user enters an on-center (oC) for the rebar spacing, which defaults to 18".
• The user can also input an inset (i) for the distance from the side of the slab to the first row of the rebar grid,  The inset has a default of 3".
• The user can specify the number of mats (m).  The default is one.
• The user can specify the length of the pre-cut reinforcement bars being used (rL) which is used to determine if lapping is required.
• The user can specify the size of rebar (rS).  This is the size of rebar which is used to compute the diameter for lapping considerations.
• The user can specify the lapping factor(lF).  This is the multiple of the diameter of the rebar to specify the lapping distance.  40 (default) and 60 are common.

## Description

This calculator computes the length of a simple rectangular grid of rebar. Rebar Specifications   It employs lapping for dimensions (length or width) in excess of the user specified rebar lengths (rL: see Lapping below).  A tolerance for determining the need for an extra rebar is set to less than one inch  for a spacing fraction above the tolerance.

### Lapping

When the dimensions of your slab or wall exceed the length of a single piece of rebar, it is required to lap bars and tie 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