Professional Steel Reinforcement Estimator & Cost Analyzer
6 mm
8 mm
10 mm
12 mm
16 mm
20 mm
25 mm
32 mm
40 mm
50 mm
Select the standard metric diameter of the steel bar.
Standard commercial length is often 12m.
Please enter a valid positive length.
Total number of bars required.
Please enter a valid quantity (at least 1).
Current market price per metric tonne (1000 kg).
Please enter a valid positive price.
Total Estimated Weight
0 kg
Based on formula: (D² / 162) × Length
Unit Weight0 kg/m
Total Weight (Tonnes)0 MT
Total Material Cost0.00
Comparison of Total Weight for Different Diameters (Same Length & Qty)
Parameter
Value
Unit
Breakdown of calculation parameters and results.
What is a Rebar Weight Calculator Metric?
A rebar weight calculator metric is an essential tool for civil engineers, quantity surveyors, and construction professionals. It allows users to determine the theoretical mass of steel reinforcement bars based on their diameter and length. In the metric system, this calculation is critical for ordering materials, estimating transportation costs, and verifying supplier invoices.
Unlike generic volume calculators, a rebar weight calculator specifically applies the density of mild steel (approximately 7850 kg/m³) to standard bar geometries. This tool is designed for anyone involved in structural concrete work, from large infrastructure projects to residential foundations.
Common Misconception: Many believe that rebar weight varies significantly by manufacturer. In reality, manufacturing standards (like BS 4449 or ASTM A615) impose strict tolerance limits, making the theoretical formula highly accurate for estimation purposes.
Rebar Weight Calculator Metric Formula
The industry-standard formula used to calculate the weight of deformed steel bars in the metric system is derived from the volume of a cylinder multiplied by the density of steel.
The Simplified Formula
For on-site calculations and quick estimations, the following simplified formula is universally accepted:
W = (D² / 162) × L
Where:
W = Total Weight in Kilograms (kg)
D = Diameter of the bar in millimeters (mm)
L = Total Length of the bar in meters (m)
162 = A constant derived from steel density (approx. 162.19 to 162.28)
Variables Table
Variable
Meaning
Unit
Typical Range
D
Nominal Diameter
Millimeters (mm)
6mm – 50mm
L
Length per Bar
Meters (m)
6m – 12m (Stock lengths)
ρ (Rho)
Steel Density
kg/m³
7850 kg/m³
Key mathematical variables used in rebar calculations.
Practical Examples
Example 1: Residential Column Reinforcement
A contractor needs to order reinforcement for 10 concrete columns. Each column requires 8 bars of 16mm diameter, each cut to 3.5 meters in length.
Input Diameter: 16 mm
Total Length per Bar: 3.5 m
Quantity: 10 columns × 8 bars = 80 bars
Step 1: Calculate Unit Weight
Weight per meter = 16² / 162 = 256 / 162 ≈ 1.58 kg/m
Step 2: Calculate Total Weight
Total Weight = 1.58 kg/m × 3.5 m × 80 bars = 442.4 kg
Financial Implication: If steel costs $850/tonne, this order would cost approximately $376.
Example 2: Slab Foundation Mesh
An engineer is estimating the steel for a slab. The design calls for 10mm bars. The total running meter length required (sum of all bars) is 2,500 meters.
Input Diameter: 10 mm
Total Length: 2,500 m (cumulative)
Quantity: 1 (treated as one bulk batch)
Calculation:
Unit Weight = 10² / 162 = 100 / 162 ≈ 0.617 kg/m
Total Weight = 0.617 × 2,500 = 1,542.5 kg (or 1.54 Tonnes)
How to Use This Rebar Weight Calculator Metric
Select Diameter: Choose the standard bar size from the dropdown menu (e.g., 12mm).
Enter Length: Input the length of a single bar or the total running meters required.
Input Quantity: Enter the number of bars. If you entered the total running length in step 2, keep this as 1.
Check Cost (Optional): Enter the current market price per tonne to get an immediate cost estimate.
Analyze Results: View the total weight in kg and tonnes, and use the dynamic chart to see how changing the diameter would impact the total weight.
Key Factors That Affect Rebar Weight Results
When using a rebar weight calculator metric, several real-world factors can influence the final figures compared to theoretical calculations:
Rolling Tolerance: Steel mills have a manufacturing tolerance (often ±3% to ±5%). A bar might be slightly heavier or lighter than the theoretical standard depending on the rolling process.
Steel Grade Density: While 7850 kg/m³ is standard, specialized alloys or stainless steel rebar may have slightly different densities.
Corrosion and Rust: Heavily rusted bars may lose cross-sectional area, reducing weight, or have added mass from oxidation layers, though this is usually negligible for weight estimation but critical for structural integrity.
Lapping and Wastage: This calculator gives the net weight. In practice, you must add 10-15% for overlaps (splices) and cutting wastage.
Cost Fluctuations: The financial output depends heavily on global steel market rates, fuel costs for transport, and local tariffs.
Coating Weight: Epoxy-coated or galvanized rebar includes the weight of the coating, adding a small percentage to the total mass.
Frequently Asked Questions (FAQ)
Why is the constant 162 used in the formula?
The constant 162 is derived mathematically: 7850 kg/m³ / (1000² / (π/4 * 1000)). It simplifies the calculation so you only need the diameter in mm to get weight in kg/m.
Can I use this for Imperial sizes?
No, this is a rebar weight calculator metric. Imperial bars (#3, #4, etc.) use different diameter standards and require a different formula variant.
Does this calculate the weight of TMT bars?
Yes, Thermo-Mechanically Treated (TMT) bars generally follow standard ISO/BS diameters and densities, so the formula applies accurately.
How do I convert the result to Tonnes?
The calculator does this automatically. To do it manually, divide the result in kilograms by 1,000.
What is the standard length of a rebar?
In most metric countries, rebar is sold in standard stock lengths of 12 meters to fit on transport trailers. Some suppliers offer 6m or 9m lengths.
Should I include the ribs in the diameter measurement?
No, the diameter refers to the "nominal diameter" of the core bar, exclusive of the deformations (ribs/lugs). Use the specified size (e.g., 12mm) rather than caliper measurements.
Is the calculated weight the same as the shipping weight?
Theoretical weight is close, but shipping weight is determined by the weighbridge. The rolling tolerance means actual weight can vary by ±4%.
Does this tool help with bending schedules?
This tool calculates mass only. For bending schedules, you need to calculate the cut length of each shape before summing them up here.
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