Steel Coil Size Language Cheat Sheet — Global Terminology Guide

Steel coil is traded globally — but the language is not global.

The same coil may be described differently in:

USA
UK
Europe
Middle East
Asia
Australia

Misunderstanding terminology leads to:

Thickness disputes
Weight miscalculation
Machine overload
Freight problems
Contract disagreements

This page is a practical cheat sheet for understanding coil size language across markets.

If you sell or buy coil internationally, this is essential reading.

1. Thickness Language (Global Differences)

mm (millimeters)

Used in:

Europe
Asia
Middle East
Africa

Example:
0.60 mm BMT

This is the safest global language.

Inches (decimal)

Used in:

USA
Some heavy industry globally

Example:
0.0236"

Always confirm decimal accuracy.

Gauge (US)

Used in:

US roofing
US fabrication

Example:
24 gauge

Must clarify:

Material type
Gauge chart

Gauge is not universal.

SWG (UK)

Standard Wire Gauge
Used in older UK markets.

Example:
24 SWG ≈ 0.56 mm

Always convert to mm in contracts.

BWG (Tube Industry)

Birmingham Wire Gauge
Used in tube and pipe wall thickness.

Example:
16 BWG wall

Never assume same as sheet gauge.

2. Base Metal vs Total Thickness

BMT (Base Metal Thickness)

Steel only, no coating.

Used in:

Structural calculation
Roofing in Australia
Engineering documentation

Critical for compliance.

TCT (Total Coated Thickness)

Steel + zinc + paint.

Used in:

Some roofing markets
Some Asian mills

Dispute risk if unclear.

Always specify which one applies.

3. Coating Language

Z (Galvanized)

Z100, Z180, Z275
Grams per square meter zinc.

Used in:

Europe
Middle East
Africa
Asia

G (US Galvanized)

G90, G60 etc.

Ounces per square foot.

Used in:

Z and G are not directly interchangeable without conversion.

AZ / Al-Zn

Galvalume coating.

AZ150 etc.

Used globally.

PPGI / PPGL

Prepainted galvanized or galvalume.

Common in:

Asia
Export markets

Terminology varies.

4. Weight Language (High Risk Area)

kg

Global standard.

Safest unit.

Metric Tonne (t)

1,000 kg.

Used in international trade.

US Ton (Short Ton)

2,000 lb (~907 kg)

Used in USA domestic trade.

UK Ton (Long Ton)

2,240 lb (~1,016 kg)

Used historically in UK.

“Ton” must always be clarified.

5. Coil Geometry Terms

ID (Inner Diameter)

Mandrel size.

Common:
508 mm
610 mm
762 mm

Must match uncoiler.

OD (Outer Diameter)

Full coil diameter.

Affects:

Brake load
Container fit
Storage

Core Type

Paper core
Steel core

Important for hydraulic expansion.

6. Width Language

mm

Most common globally.

Example:
1000 mm

Inches

Common in US markets.

Example:
48”

Master Coil

Full width mill coil.

Slit Coil

Narrowed coil from slitting process.

Important in tube mills.

7. Shape & Flatness Terms

Camber

Sideways bow.

Coil Set

Longitudinal curvature.

Crown

Thickness variation across width.

Buckle / Waviness

Flatness defect.

Language differs slightly by region.

8. Structural Strength Language

MPa

Metric strength unit.

Used globally outside US.

PSI / KSI

Used in US.

1 MPa ≈ 145 PSI

Always confirm unit.

9. Tolerance Language

±0.03 mm

Symmetrical tolerance.

+0 / –0.05 mm

Minimum thickness guarantee.

Common in structural work.

Nominal Thickness

Target thickness.

Not exact thickness.

10. Commercial Language Differences

Term	Region	Meaning
GI	Global	Galvanized Iron (actually steel)
CRC	Asia	Cold Rolled Coil
HR	Global	Hot Rolled
HDG	US	Hot Dip Galvanized
Prime	Global	First-quality material
Secondary	Global	Downgraded coil

Trade language varies more than engineering language.

11. High-Risk Words in International Trade

Avoid ambiguity in:

“Gauge”
“Ton”
“Nominal”
“Coated thickness”
“Standard”
“Commercial quality”

Always define in measurable units.

12. Safe International Specification Template

Thickness: 0.60 mm BMT
Tolerance: ±0.03 mm
Width: 1000 mm ±1 mm
Coating: Z275
Weight: 5,000 kg
ID: 508 mm
Max OD: 1500 mm

Clear, measurable, global.

No ambiguity.

13. Why Terminology Confusion Causes Disputes

Misunderstanding language leads to:

Under-thickness claims
Wrong gauge delivery
Machine overload
Freight miscalculation
Structural rejection

Most coil disputes are language disputes — not quality disputes.

14. FAQ Section

Is gauge universal?

No.

Is ton the same everywhere?

No.

Does 0.60 mm always mean base metal?

Not unless specified.

Is Z275 same worldwide?

Yes, but US uses different unit system.

Should contracts use mm?

Yes.

Should weight be in kg?

Yes.

Is BMT critical for structural?

Yes.

Should ID be specified?

Always.

Is “GI” technically iron?

No, it’s steel.

Is terminology standardized globally?

No — but measurable units are.

15. Conclusion

Steel coil is global.

Its language is not.

Understanding terminology prevents:

Mechanical failures
Commercial disputes
Freight mistakes
Warranty problems

The safest international language is:

mm
kg
metric tonnes
MPa
Explicit coating designation
Explicit ID and OD

Engineering must use measurable units — not trade slang.