`W_"rebar" = 1 % * L * W * D * 7850 "kg/"m^3`

Enter a value for all fields

The Rebar Rough Estimate by Percentage of Rebar in Slab calculator estimates the total weight  Concrete Slab with one Rebar Grid mat of reinforcement bars (rebar) needed for a concrete slab based on the dimensions of the slab and a percent of the slab volume in steel rebar, and a density of steel of 7,850 kg/m³.

INSTRUCTIONS: Choose units and enter the following:

• (P) Percent of Slab Volume in Rebar (1% default)
• (L) Length of Slab
• (W) Width of Slab
• (D) Depth of Slab

Weight of Rebar (W):  The weight of rebar is returned in kilograms.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

The Rebar Rough Estimate by Percentage of Rebar in Slab is:

           W_rebar = P • L • W • D • ρ_steel

where:

• W_rebar is the rough estimate of the weight of rebar in a slab
• P is the percentage volume of the slab that is rebar (default is 1%)
• L is the length of the slab
• W is the width of the slab
• D is the depth of the slab
• ρ_steel is the mean density of steel

Rebar and Slab Calculators:

• Compute the Length of Rebar needed for a slab. - This is an accurate engineering tool to compute the length of rebar in a rectangular grid based on all of the key specifications (rebar size, number of mats, lapping factors and more).
• Compute the Weight of Rebar in a slab. This is an accurate engineering tool to compute the weight of rebar in a rectangular grid based on all of the key specifications (rebar size, number of mats, lapping factors and more).
• Compute the Surface Area of a slab.
• Compute the Surface Area of Concrete Forms. 
• Compute the Volume of Concrete in a slab. 
• Compute the Total Weight of a Slab with Rebar
• Spanish Version: Calculadora de Barras de Refuerzo

Attribution

Thanks to Mithil Haldakar for the description of this estimation method in his answer in Quora.