The Rebar and Concrete in a Slab calculator computes the total length and weight of rebar and the volume of concrete needed for a slab.
INSTRUCTIONS: Choose units and enter the following:
- (L) Length of the slab
- (W) Width of the slab
- (D) Depth of slab
- (rS) Rebar Size (2,3,4,5,6,7,8,9,10,11,12,14,16,18,20)
- Use Size "0" for No Rebar
- (oC) On-center spacing Rebar
- (i) Inset distance from edge of slab
- (M) Number of mats
- (RL) Length of the pre-cut rebar sticks
- (LF) Lapping Factor. 40 (default) and 60 are common.
Rebar and Concrete in a Slab: The calculator returns:
- Total Length of rebar in feet.
- Total Weight of rebar in pounds.
- Estimated Rebar Cost in U.S. dollars
- Total Volume of concrete in cubic yards. Note: this accounts for the concrete displaced by rebar.
- Total Weight of Slab in pounds. Note: this includes the weight of rebar and concrete, and takes into consideration the concrete displaced by rebar.
However, the above can be automatically converted to compatible units via the pulldown menu.
See the Rebar Calculator for more concrete and rebar functions and features. VIDEO INSTRUCTION
Rebar and Slab Calculators:
- Rebar and Concrete in a Slab: The calculator returns all of the following:
- Total Length of rebar in feet
- Total Weight of rebar in pounds
- Total Volume of concrete in cubic yards. Note: this accounts for the concrete displaced by rebar.
- Total Weight of Slab in pounds. Note: this includes the weight of rebar and concrete.
- Length of Rebar in Grid
- Weight of Rebar in Grid
- Rebar in a Wall
- Rebar in an Irregular Shaped Slab
- Rebar in a Circular Slab
- Rebar Lapping Length
- Rebar Cost Estimate
- Weight of Length of Rebar
- Concrete Displaced by Rebar
- Compute the Total Weight of a Slab with Rebar
- Spanish Version: Calculadora de Barras de Refuerzo
The Math / Science
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The rebar algorithm calculates the length of rebar in the grid based on the slab dimensions, spacing, inset, number of mats, rebar size and lapping factor. Based on the rebar length and size, the weight of rebar is computed. Based on the slab dimensions and the volume displaced by rebar, the volume of concrete is computed.
Rebar Usage
Reinforcement bars are often used in concrete including common slabs. This formula provides a length and weigh calculation that is useful in understanding the additional load of the slab added by the rebar steel. It is also useful for calculating the weight of rebar when considering transport. Steel is dense and heavy. Most vehicles would be considerably overloaded in weight of rebar long before their potential volume is full, which poses a significant safety issue. In the U.S., most pickup trucks are rated at a half or three quarters ton load rating. This rating indicates the safe weight of a load that can be carried. The rebar weight formula can help determine how many trips are required to transport the load of reinforcement steel safely.
This is useful for:
- The determination of bar length in concrete slab
- The weight of rebar in concrete slab
Lapping Length
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 pre-cut rebar is 40' and 60' in the United States.
See Also
- Total Slab Weight - This includes the weight of the rebar and the concrete.
- Brick or Block Wall - Number of brick or block needed for a wall.
- Foundation - Poured - Amount of concrete needed for a poured foundation.
- Foundation - Block - Number of blocks needed for a foundation.