Calculate the exact weight of Hexagonal Bars (Hex Bars) in Mild Steel (MS), Stainless Steel (SS), and Brass instantly with our free online calculator. Simply enter your across-flats dimension and length in mm or inches, and get accurate results in both kg and lbs.

Weight Calculation for Hex Bar

The weight of a Hex Bar (also known as a Hexagon Bar or AF Bar) is determined by its cross-sectional area, length, and material density. Hex bars are widely used in machining for bolts, nuts, shafts, and decorative metalwork due to their unique six-sided geometry which provides excellent grip for tools. The standard density for Mild Steel is 7.85 g/cm³, while Stainless Steel and Brass have different densities that affect the final weight. Accurate weight calculation is critical for material procurement, machining stock planning, and precise cost estimation in engineering projects.

Hex Bar Weight Formula and Manual Calculation

The industry-standard formula for calculating hex bar weight uses the "Across Flats" (AF) dimension. The geometric constant for a regular hexagon is derived from (3√3) / 2 ≈ 2.598.

Step 1: Calculate Cross-Sectional Area (mm²)

Area = 0.866 × Across Flats² (mm)

Step 2: Calculate Weight (kg)

Weight (kg) = Area (mm²) × Length (m) × Density Factor

Density Factors for common materials:
0.00000785 for Mild Steel (MS)
0.00000793 for Stainless Steel (SS 304/316)
0.00000850 for Brass
0.00000896 for Copper

Simplified Formula for MS Hex Bar:
Weight (kg) = Across Flats² (mm) × Length (m) × 0.00000680

For imperial units (inches and lbs):

Weight (lbs) = Across Flats² (in) × Length (ft) × 2.95 (for Steel)

Step-by-Step Calculation Example

  • Step 1: Identify dimensions: Across Flats (AF) = 20 mm, Length = 2 m (Mild Steel)
  • Step 2: Calculate Area Factor: 0.866 × 20² = 0.866 × 400 = 346.4 mm²
  • Step 3: Apply density factor: 346.4 × 2 × 0.00000785
  • Step 4: Result: 692.8 × 0.00000785 = 5.44 kg
  • Step 5: Compare with Brass: 5.44 × (8.50/7.85) ≈ 5.89 kg

This calculation aligns exactly with the results provided by the hex bar weight calculator.

Metal Hex Bar Weight Chart (Quick Reference per Metre)

Size AF (mm) Mild Steel (kg/m) Stainless Steel (kg/m) Brass (kg/m)
10 mm0.68 kg0.69 kg0.73 kg
12 mm0.98 kg0.99 kg1.06 kg
16 mm1.74 kg1.76 kg1.88 kg
20 mm2.72 kg2.75 kg2.94 kg
25 mm4.25 kg4.30 kg4.60 kg
30 mm6.12 kg6.20 kg6.63 kg
40 mm10.88 kg11.01 kg11.78 kg

Frequently Asked Questions

What is the formula for Hex Bar weight?

The formula for Hex Bar weight is: Weight = 0.866 × Across Flats² (mm) × Length (m) × Density Factor. For Mild Steel, you can use the simplified constant: AF² × Length × 0.00000680 to get the weight in kg.

How much does a 20mm MS Hex Bar weigh per meter?

A standard 20mm Mild Steel Hex Bar weighs approximately 2.72 kg per metre. This is calculated using the formula: 0.866 × 20² × 0.00000785 = 2.72 kg. Brass hex bars of the same size will weigh slightly more at around 2.94 kg/m.

What is the difference between Across Flats and Across Corners?

"Across Flats" (AF) is the distance between two parallel flat sides of the hexagon, which is the standard measurement for sizing hex bars and nuts. "Across Corners" is the distance between two opposite vertices. The weight calculator uses the Across Flats dimension as it is the industry standard for specifying hex stock.