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📐 The Core Density Formula
When working with metal plates or rods, you translate dimensional measurements (length, area, pieces) into weight units (kg or lb) using the material's density (ρ) as a conversion factor.
Mass (m) = Volume (V) × Density (ρ)
🔵
Mild Steel
7,850 kg/m³
⚪
Stainless Steel
7,900 kg/m³
🪨
Cast Iron
7,200 kg/m³
🔶
Aluminium
2,700 kg/m³
🟠
Copper
8,960 kg/m³
🟡
Brass
8,500 kg/m³
🟦 Plate (Rectangular Solid) Calculator
A plate is a rectangular solid. Volume = Length × Width × Thickness
Vplate = L × W × T | All dimensions in metres
Mass = L (m) × W (m) × T (m) × ρ (kg/m³)
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🔵 Rod / Bar (Cylindrical) Calculator
A solid rod is a cylinder. Volume = π × r² × Length = (π × d²/4) × Length
Vrod = π × (d/2)² × L | Diameter in mm, Length in metres
Mass = π × (D/2000)² × L × ρ [D in mm, L in m, ρ in kg/m³]
📋 Common Steel Rod Weight Reference (Mild Steel 7,850 kg/m³)
| Diameter (mm) | kg per metre | kg per 6m bar | kg per 12m bar |
|---|
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🏭 ERP / SAP Unit of Measure Mapping
When mapping physical material quantities into an ERP system like SAP (ECC or S/4HANA), establish a Base Unit of Measure and Alternative Units of Measure in the Material Master.
Best Practice: Use KG (Kilogram) as the Base UoM for metals — valuation and purchasing are done by weight.
Alternative UoMs to maintain in MM01/MM02 → Additional Data → Units of Measure:
| Alt UoM | Used For | Example Ratio | SAP Field |
|---|---|---|---|
| PC (Piece) | Inventory counting, GI to shop floor | 1 PC = 157 KG (2m×1m×10mm plate) | MARA-MEINS |
| M (Metre) | Rod / bar purchasing by length | 1 M = 2.46 KG (20mm rod) | Additional UoM tab |
| M2 (Sq. Metre) | Plate area-based ordering | 1 M2 = 78.5 KG (10mm thick) | Additional UoM tab |
Batch-Specific UoM: For materials where density varies per batch (alloys, porous materials), use Batch-Specific Units of Measure or Active Ingredient Management in SAP so the conversion ratio is tied to specific batch characteristics.