The Key Starting Point — Stainless Steel Density
Carbon steel has a density of approximately 7.85 g/cc. Stainless steel is slightly denser at 7.93 g/cc. This difference — small as it sounds — means stainless bars weigh about 1% more than equivalent carbon steel bars. All the formulas below use the stainless steel density of 7.93 g/cc.
When a supplier quotes weight, verify they are using 7.93 g/cc (or 7930 kg/m³) — not the carbon steel figure.
Formula 1 — Round Bar
The weight per metre of a round bar depends only on its diameter.
Formula: kg/m = D² × 0.006233
Where D is the diameter in millimetres.
Worked Example: 25mm diameter round bar:
kg/m = 25 × 25 × 0.006233 = 3.895 kg/m
For a 6-metre bar: 3.895 × 6 = 23.37 kg
For a bundle of 50 bars × 6 metres: 50 × 23.37 = 1,168.5 kg ≈ 1.17 MT
Formula 2 — Hex Bar
For hexagonal bars, the dimension used is Across Flats (AF) — the distance between two opposite flat faces. This is the same as the wrench size.
Formula: kg/m = AF² × 0.006868
Where AF is the across-flats dimension in millimetres.
Worked Example: 27mm AF hex bar:
kg/m = 27 × 27 × 0.006868 = 5.01 kg/m
For a 3-metre bar: 5.01 × 3 = 15.03 kg
Formula 3 — Square Bar
Formula: kg/m = S² × 0.007930 / 1000
Where S is the side dimension in millimetres.
Worked Example: 25mm square bar:
kg/m = 25 × 25 × 7.930 / 1000 = 4.956 kg/m
Formula 4 — Flat Bar
Flat bars have two dimensions: width (W) and thickness (T).
Formula: kg/m = W × T × 0.00793
Where W and T are both in millimetres.
Worked Example: 50mm wide × 6mm thick flat bar:
kg/m = 50 × 6 × 0.00793 = 2.379 kg/m
For a 6-metre flat bar: 2.379 × 6 = 14.27 kg
Formula 5 — Angle Bar
Equal angle bars have leg length (A) and thickness (T).
Formula: kg/m = T × (2A − T) × 0.00793
Where A is the leg length and T is the thickness, both in millimetres.
Worked Example: 50mm × 50mm × 5mm angle:
kg/m = 5 × (2×50 − 5) × 0.00793 = 5 × 95 × 0.00793 = 3.766 kg/m
For a 6-metre angle: 3.766 × 6 = 22.6 kg
Converting to Pieces from MT
A common practical question: "I need 1 MT of 25mm round bar in 6-metre lengths — how many pieces is that?"
Step 1: Weight per bar = 3.895 kg/m × 6m = 23.37 kg per bar
Step 2: Number of bars = 1000 kg ÷ 23.37 = 42.8 bars ≈ 42 full bars
Note: Always round down when the question is "how many complete pieces fit in X weight."
Tolerance on Theoretical Weight
The weights calculated by these formulas are theoretical weights based on nominal dimensions. Actual weights will vary due to:
- Dimensional tolerance: Bars are produced to size tolerances per IS 6911. A 25mm bar might actually be 24.8mm or 25.2mm in places.
- Length tolerance: Standard lengths have +/- tolerances.
- Density variation: Minor heat-to-heat composition variation affects density slightly.
In practice, expect actual weight to be within ±3% of theoretical weight. For billing purposes, commercial practice in India is to bill on actual weighed weight — a properly calibrated weighbridge ticket should accompany every major consignment.
Use Our Free Online Calculator
Rather than calculating by hand, use our free Stainless Steel Weight Calculator. It calculates weight for round bar, hex bar, flat bar, square bar, angle bar, and channel — in mm, cm, inch, or feet. Results in kg and lbs. Includes a complete size reference table from 2mm to 150mm.