GI Sheet Price Per Ton Explained: The Difference Between Theoretical Weight and Actual Weight
2026-06-20
Introduction
When purchasing galvanized steel sheets (GI Sheets), buyers often encounter two pricing methods:
- Theoretical Weight Pricing
- Actual Weight (Scale Weighing) Pricing
Understanding the difference is critical to avoid hidden losses in bulk steel procurement.
1. What Is Theoretical Weight?
Theoretical weight is calculated based on nominal dimensions:
- Thickness
- Width
- Length
It is a mathematical estimation used in quotation and invoicing.
2. What Is Actual Weight?
Actual weight refers to the real measured weight using industrial scales at:
- Steel factory
- Port warehouse
- Logistics terminal
Standard coating system:
- Top coat: 15–25 μm
- Back coat: 5–12 μm
👉 This is the most accurate measurement of delivered steel.
3. Why Weight Differences Occur (Thickness Tolerance Issue)
Steel production follows international tolerance standards:
Example:
- Ordered thickness: 0.50mm
- Actual production: 0.47–0.50mm
If invoiced based on theoretical weight, buyers may unknowingly pay for "non-existent steel weight".
4. GI Sheet Weight Calculation Formula
Standard formula:
Weight (kg) = Thickness (mm) × Width (m) × Length (m) × 7.85
Where:
- 7.85 = density of steel
- Zinc coating may require adjustment for high coatings (e.g., Z275)
5. How to Avoid Overpaying in GI Sheet Purchase
1) Confirm pricing basis in contract
Always specify:
- " Based on Actual Weight "
- " Based on Theoretical Weight "
2) Control thickness tolerance
Request tighter tolerance when pricing is based on theoretical weight:
- Standard: ±0.03–0.05mm
- Recommended: ±0.01mm
3) Optimize zinc coating selection
Do not over-reduce zinc coating:
- Z40: low cost, short lifespan
- Z120–Z275: suitable for outdoor and coastal environments
Conclusion
Understanding weight calculation methods helps buyers:
✅Avoid hidden cost loss
✅Improve procurement transparency
✅Ensure fair pricing
Always clarify weight basis before confirming orders.
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