Estimate steel reinforcement weight, cost, and load requirements instantly.
Imperial (Feet/Lbs)
Metric (Meters/Kg)
Select your preferred measurement standard.
Standard diameter designation.
Please enter a valid positive length.
The length of a single piece of rebar.
Please enter a valid positive integer.
Total number of bars needed.
Cost per lb or per kg for financial estimation.
Total Weight
0 lbs
Weight Per Bar
0 lbs
Total Length
0 ft
Estimated Cost
$0.00
Formula Used:Total = (Unit Weight) × Length × Quantity
Rebar Specification Breakdown
Parameter
Value
Unit
Detailed breakdown of the current calculation parameters.
Weight Comparison: Selected Size vs. Alternatives
Graph showing the total weight of your order compared to one size smaller and one size larger.
What is a Weight of Rebar Calculator?
A weight of rebar calculator is an essential tool for civil engineers, contractors, and construction estimators. It allows professionals to precisely determine the total mass of steel reinforcement bars required for a concrete project. By inputting the diameter (size), length, and quantity of the bars, the calculator computes the total tonnage, which is critical for ordering materials, arranging logistics, and calculating structural loads.
Reinforcing bar, or "rebar," is sold by weight, not just length. Therefore, understanding the total weight is directly linked to the financial cost of the project. Whether you are building a small foundation or a massive skyscraper, accurate steel estimation prevents material shortages and budget overruns.
This tool is designed for structural engineers, site managers, and quantity surveyors who need to convert linear schematics into purchasing lists and load manifests quickly.
Weight of Rebar Calculator Formula and Math
The calculation relies on standard density properties of carbon steel (approximately 7850 kg/m³ or 490 lbs/ft³). The mathematical derivation depends on whether you are using the Imperial or Metric system.
Metric Formula:
W = (D² / 162.2) × L × Q
Imperial Estimation:
W = Unit Weight (lb/ft) × L × Q
Where:
Variable
Meaning
Typical Unit
Typical Range
W
Total Weight
kg or lbs
10 – 100,000+
D
Diameter of Rebar
mm (Metric)
6mm – 57mm
L
Length per Bar
m or ft
6m, 12m, 20ft, 40ft
Q
Quantity
Pieces
1 – 10,000+
Practical Examples
Example 1: Residential Foundation (Imperial)
A contractor needs to order steel for a home foundation. The plans call for 150 pieces of #4 rebar, each 20 feet long.
Rebar Size: #4 (0.500 inches)
Unit Weight: ~0.668 lbs/ft
Calculation: 0.668 lbs/ft × 20 ft × 150 pieces
Total Weight: 2,004 lbs
Financial Impact: At $0.50/lb, the steel cost is approximately $1,002.
Example 2: Commercial Column (Metric)
An engineer is designing a concrete column requiring dense reinforcement using 25mm bars. They need 40 bars of 12 meters each.
Rebar Size: 25mm
Unit Weight: ~3.853 kg/m
Calculation: 3.853 kg/m × 12 m × 40 pieces
Total Weight: 1,849.44 kg
Logistics Note: This weight is nearly 2 tonnes, requiring a standard flatbed truck for delivery.
How to Use This Weight of Rebar Calculator
Select Unit System: Choose between Imperial (US Standard) or Metric based on your project blueprints.
Choose Rebar Size: Select the standard size designation (e.g., #4 or 12mm) from the dropdown menu.
Enter Length: Input the length of a single bar. Common stock lengths are 20ft, 40ft, 6m, or 12m.
Enter Quantity: Input the total number of bars required.
Add Price (Optional): If you know the current market price per unit of weight (lb or kg), enter it to get a cost estimate.
Analyze Results: View the total weight in the highlighted box and review the comparison chart to see how changing the bar size would affect the total load.
Key Factors That Affect Rebar Weight Results
Nominal vs. Actual Diameter: Standard weights are based on nominal diameters. Deformation ridges on rebar add slight volume, but weight is calculated on the theoretical smooth cylinder equivalent.
Steel Density Variations: While 7850 kg/m³ is standard, alloy additives for corrosion resistance (like stainless steel rebar) can slightly alter density.
Lap Splices: In real-world construction, bars must overlap to maintain structural continuity. A weight of rebar calculator usually calculates net length. You must add 10-15% extra for lap splices manually.
Waste and Off-cuts: Standard stock lengths (e.g., 20ft) often result in waste if your required length is 18ft. The calculated weight is the installed weight, not the purchased weight including waste.
Coating Weight: Epoxy-coated rebar (green bar) has a negligible weight increase from the coating, but it significantly affects the cost per ton.
Rolling Tolerances: Manufacturing standards (ASTM A615) allow for small deviations in weight per foot (approx +/- 6%). For massive projects, this tolerance can add up to significant tonnage differences.
Frequently Asked Questions (FAQ)
Why is rebar sold by weight?
Steel mills produce rebar in bulk tonnage. Pricing and shipping logistics are universally handled by mass because volume is difficult to measure accurately for bundled irregular shapes.
Does this calculator include the weight of epoxy coating?
No, the calculator uses the theoretical mass of bare black steel. Epoxy adds minimal weight but should be considered for cost.
What is the difference between #4 and 12mm rebar?
They are roughly equivalent. #4 is an Imperial designation (4/8ths or 0.5 inch diameter), while 12mm is a soft metric conversion often used in international projects.
How accurate is the theoretical weight formula?
The formula $D^2/162$ is an approximation derived from steel density. It is generally accurate to within 1-2% of ASTM standard table weights.
Can I calculate weight for stainless steel rebar?
Yes, stainless steel has a very similar density to carbon steel, so this weight of rebar calculator remains accurate for stainless variants.
Does the length include bends and hooks?
You should input the total developed length (straight length + length of hooks/bends) to get an accurate weight.
What is the standard density of steel used?
The standard density used is 490 lbs per cubic foot (Imperial) or 7850 kg per cubic meter (Metric).
How do I estimate the cost of rebar?
Multiply the Total Weight result from this calculator by your local supplier's price per lb or per ton.