Leather Thickness Conversion Chart: Ounces, Millimeters & Irons

Quick answer: In leatherworking, 1 ounce (1 oz) represents approximately 1/64 inch, or about 0.4 mm, of leather thickness. Because leather is a natural material, its actual thickness may vary slightly across a hide and between suppliers.

Leather Thickness Conversion Chart

Use this chart as a practical reference when comparing leather specified in ounces, millimeters or inches.

What Does “oz” Mean in Leather?

For leather, ounces describe thickness rather than the total weight of a finished product. One ounce is approximately 1/64 inch or 0.4 mm.

A specification such as 4–5 oz means the leather is expected to measure approximately 1.6–2.0 mm. A range is normally used because natural hides are not perfectly uniform.

What Does “Iron” Mean?

“Iron” is an older leather and shoemaking thickness term. It is not applied consistently by every country, supplier or industry. English and French or Paris iron systems may refer to different measurements.

How to Choose Leather Thickness

Wallets and card holders

Wallet interiors commonly use thinner leather to reduce bulk, while the exterior may use slightly thicker leather for structure and durability. The final thickness also depends on the number of folded and stitched layers.

Leather bags

Small and soft bags often use leather around 1.2–1.8 mm. More structured bags may require thicker leather, reinforcement or a combination of outer leather, lining and support materials.

Belts and straps

Belts and load-bearing straps generally require thicker leather than wallets or soft bags. The correct thickness depends on the leather type, intended load, construction and whether multiple layers are laminated together.

Notebook covers and tech cases

Medium-weight leather is often suitable for covers and cases, but edges, folds, closures and device protection requirements may call for selective skiving or reinforcement.

Why Actual Leather Thickness Can Vary

Leather is a natural material, so its thickness can vary across different areas of the same hide. Splitting and shaving improve consistency, but some variation may remain.

Manufacturing processes also change the effective thickness:

• Splitting: reduces an entire hide or section to a target thickness.
• Shaving: improves thickness accuracy and consistency.
• Skiving: thins selected areas for folds, seams and cleaner edges.
• Lining and reinforcement: add thickness to the completed construction.
• Adhesives and multiple layers: can make the finished component significantly thicker than the outer leather alone.

Practical Leather Ordering Checklist

• Use millimeters as the primary production measurement.
• Add the ounce range as a reference when appropriate.
• Confirm whether thickness is measured before or after finishing.
• Define an acceptable thickness tolerance with the supplier.
• Check several areas of the hide instead of relying on one measurement.
• Evaluate the total layered construction, not only the outer leather.
• Approve a physical sample before bulk production.

Example Specification

Related Leather Resources

• Leather Types Guide for Custom Leather Goods
• Custom Leather Goods Manufacturer
• Custom Leather Wallet Manufacturing

References

• Tandy Leather: Leather Weight and Thickness Chart
• Weaver Leather Supply: Leather Thickness Chart
• Weaver Leather Supply: Understanding Leather Weights

This chart is a practical reference rather than a substitute for measuring the actual leather. Always confirm the production specification with your leather supplier or manufacturer.