Total rebar length
Calculate individual pieces or bars distributed across a surface.
Rebar Calculator
Calculate reinforcing bar quantity, total length, approximate weight and commercial bars. You can also estimate reinforcement distributed by spacing for slabs, walls and other surfaces.
Approximate weight
Calculate weight from bar diameter and theoretical kilograms per meter.
Commercial bars
Estimate the number of commercial bars required for the total length.
Free online tool
Rebar Calculator
Calculate rebar quantity, total length, approximate weight and steel required for slabs, walls, beams and other elements.
Bar information
Results are approximate and do not replace structural design. Bar quantity, diameter, spacing, anchorage, lap splices, concrete cover and reinforcement layout must be defined by a qualified professional and the project drawings.
How to calculate reinforcing steel
In direct mode, the number of pieces is multiplied by the length of each piece.
In spacing mode, the number of bars depends on surface dimensions, maximum spacing, reinforcement directions and number of layers.
Steel weight is calculated by multiplying the recommended total length by the theoretical weight per meter for the selected diameter.
Direct length
Length = quantity × piece length
Steel weight
Weight = total length × kg per meter
Rebar distributed across a slab
Surface information
Length5 m
Width4 m
Spacing20 cm
Directions2
Layers1
DiameterØ 10 mm
Base result
For the 5-meter bars distributed across the width:
4 ÷ 0.20 + 1 = 21 bars
For the 4-meter bars distributed across the length:
5 ÷ 0.20 + 1 = 26 bars
The base total length is approximately 209 meters before adding waste, lap splices or anchorage.
Spacing and bar quantity
The calculator rounds the number of spaces upward and adds one bar to include both edges.
This prevents the actual spacing from exceeding the entered distance.
The final distribution must be adjusted for concrete cover, edges, openings and drawing details.
Reinforcement directions and layers
One direction calculates parallel bars in a single orientation.
Two directions calculate a second family of bars perpendicular to the first.
Two layers duplicate the distribution to represent, for example, upper and lower reinforcement or reinforcement on both faces.
Theoretical weight per meter
Each bar diameter has a theoretical weight per meter. The calculator includes approximate values for bars from 6 mm to 32 mm.
Actual commercial weight may vary slightly according to standards, manufacturing tolerances and supplier.
Does not replace structural design
The calculator estimates quantities, total length and weight but does not determine the reinforcement required.
Bar diameter, spacing, concrete cover, lap splices, anchorage, minimum reinforcement and structural capacity must follow the structural drawings and calculations.
Reinforcing steel in Panama projects
Construction projects in Panama should verify available commercial diameters, bar lengths, steel specifications and structural drawing details.
Material quantities should also consider cuts, bends, hooks, lap splices, waste, transportation and storage at the construction site.
Visit MG Architecture & EngineeringRebar and reinforcing steel questions
How is the weight of reinforcing steel calculated?
Multiply the recommended total bar length by the theoretical weight per meter corresponding to the selected diameter.
How do I calculate several identical rebar pieces?
Enter the number of pieces and the length of each one. The calculator obtains the total length and applies the selected additional allowance.
How are bars calculated from a spacing value?
Divide the transverse dimension by the maximum spacing and add one bar to include both edges.
Why is the number of bars rounded up?
Rounding up prevents the actual spacing between bars from exceeding the spacing entered in the calculator.
What do one and two reinforcement directions mean?
One direction uses parallel bars in a single orientation. Two directions create a perpendicular grid commonly used in certain slabs and walls.
What do one and two reinforcement layers mean?
One layer represents one plane of reinforcement. Two layers may represent upper and lower reinforcement or reinforcement on both faces, depending on the element.
How is the number of commercial bars calculated?
The recommended total length is divided by the selected commercial bar length and the result is rounded up.
What waste allowance should I include?
A preliminary estimate may include 5% to 10%, although cuts, lap splices, anchorage and complex geometry may require a larger allowance.
Does the calculator include lap splices and anchorage?
Only through the general additional allowance. Specific development lengths, lap splices, hooks and anchorage must follow the structural design.
Does this calculator replace structural design?
No. It estimates quantities and weight but does not determine bar diameter, spacing, minimum reinforcement, concrete cover or structural capacity.