Rebar Weight Calculator
Calculate reinforcement weight for foundations and slabs.
Steel Takeoff
Reinforced Strength: The Science of Rebar
Tension & Compression
Concrete is incredibly strong in compression (pushing) but weak in tension (pulling). By embedding high-yield steel bars (rebar) into the tension zones of a concrete structure, we create a composite material that can handle massive loads.
Our **rebar weight calculator** allows you to accurately estimate the total tonnage of steel required for your project, helping with both cost estimation and logistics.
Unit Weights (kg/m)
The Danger of Corrosion
If rebar is exposed to the air or ground moisture, it will rust. As it rusts, it expands up to **four times** its original volume. This expansion force is enough to shatter the surrounding concrete from the inside out.
Always ensure you maintain the specified **concrete cover** (typically 35mm to 50mm for ground-contact concrete) and use high-quality plastic or concrete spacers to prevent the rebar from shifting during the pour.
Laps & Bends
When two bars meet, they must 'lap' (overlap) by a specific distance (usually 40 or 50 times the diameter) to ensure the tension is transferred between them. For a 12mm bar, a standard 40d lap would be 480mm.
Grade B500B
Most rebar in the UK is Grade B500B. The '500' refers to the yield strength of 500 N/mm². This steel is specifically manufactured to be easily welded and bent on site without losing its structural properties.
Pro Tip: Cutting Rebar
While rebar can be cut with an angle grinder, for large quantities we recommend hiring a **hydraulic rebar cropper**. It is significantly faster, quieter, and eliminates the risk of sparks and flying metal debris in a busy trench.
Reinforcement & Rebar FAQ
Structural Disclaimer
This calculator is for estimation of weight only. The specific quantity, diameter, and placement of rebar in any structure must be determined by a qualified structural engineer and detailed in a 'bar schedule' that complies with BS 8666.