Leather Weight & Thickness Converter
Created by: Ethan Brooks
Last updated:
Convert leather thickness between ounces, millimetres, and inches instantly. See weight class names, recommended project types, and a full reference table for choosing the right leather weight.
Leather Weight / Thickness Converter
LeathercraftConvert between ounces, millimetres, and inches instantly
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What is a Leather Weight/Thickness Converter?
A Leather Weight/Thickness Converter instantly translates between the three measurement systems used for leather thickness: ounces (oz), millimetres (mm), and inches (in). The ounce system is the North American industry standard, while metric millimetres are used internationally. This tool converts bidirectionally between all three, so you always know exactly what thickness you are working with.
Leather weight can be confusing because "ounces" in leathercraft do not refer to mass — they refer to thickness. One ounce equals 1/64 of an inch, or approximately 0.4 mm. A "6-7 oz" leather is about 2.4-2.8 mm thick, regardless of how much the hide actually weighs.
Whether you are buying leather online where the seller lists ounces, following a European pattern that specifies millimetres, or using a caliper that reads inches, this converter eliminates any confusion and recommends the best project applications for each weight.
Leather Thickness Conversion Formulas
Ounces to mm: oz x 0.396875 (or approximately oz x 0.4)
mm to ounces: mm / 0.396875 (or approximately mm / 0.4)
Ounces to inches: oz / 64 (or oz x 0.015625)
Inches to ounces: inches x 64
mm to inches: mm / 25.4
Inches to mm: inches x 25.4
The exact conversion factor is 1 oz = 1/64" = 0.396875 mm. Many quick-reference charts round to 0.4 mm per ounce, which is close enough for most practical purposes but can accumulate error at higher weights. This calculator uses the precise factor.
Conversion Example
You want to make a leather messenger bag. The pattern calls for 4-5 oz leather, but your European supplier lists thickness in millimetres. What should you order?
- 4 oz = 4 x 0.396875 = 1.59 mm
- 5 oz = 5 x 0.396875 = 1.98 mm
- You need leather in the 1.6 - 2.0 mm range
- In inches: 4 oz = 0.0625", 5 oz = 0.078"
Order leather listed as 1.6-2.0 mm from your European supplier, and it will match the 4-5 oz specification exactly.
Leather Weight Reference by Project
- 1-2 oz (0.4-0.8 mm) — Linings, book covers, garment leather, delicate goods
- 2-3 oz (0.8-1.2 mm) — Wallets, card holders, watch straps, small goods
- 3-4 oz (1.2-1.6 mm) — Handbags, totes, iPad cases, light belts
- 4-5 oz (1.6-2.0 mm) — Messenger bags, briefcases, journal covers
- 5-6 oz (2.0-2.4 mm) — Knife sheaths, light holsters, moccasins
- 6-7 oz (2.4-2.8 mm) — Holsters, heavy bags, dog collars
- 7-8 oz (2.8-3.2 mm) — Belts, tooling/carving leather, armour
- 8-10 oz (3.2-4.0 mm) — Heavy belts, saddlery, heavy-duty straps
- 10-14 oz (4.0-5.6 mm) — Sole leather, heavy saddlery, industrial
Tips for Accurate Measurement
- Measure at multiple points across the hide — thickness can vary by 0.5 mm or more from back to belly.
- Use digital calipers for precision; spring-loaded leather gauges are faster but less accurate.
- Chrome-tanned leather compresses under pressure — measure with light clamping force.
- When buying leather listed as a range (e.g. 4-5 oz), expect the actual thickness to fall anywhere in that range.
- For layered projects, add the thickness of all layers to determine total stack height for tools and hardware.
- Skiving (thinning edges) can reduce leather by 50-75% of its original thickness for folded edges.
Frequently Asked Questions
What do leather weight ounces mean?
Leather weight in ounces (oz) is an industry-standard measurement where 1 oz equals approximately 1/64 of an inch (0.4 mm) of thickness. A 5-6 oz leather is about 2.0-2.4 mm thick. This system originated in the tanning industry and remains the primary way leather is sold in North America. European and Asian suppliers typically use millimetres instead.
How do I measure leather thickness accurately?
Use a leather thickness gauge (also called a caliper or micrometre) for precise measurements. Place the leather flat and measure at multiple points since thickness can vary across a hide by 0.5 mm or more. Digital calipers reading to 0.01 mm are ideal. Avoid measuring over stamps, creases, or the edge of the hide where thickness is inconsistent.
What leather thickness do I need for my project?
Wallets and card holders: 0.8-1.2 mm (2-3 oz). Bags and totes: 1.2-1.6 mm (3-4 oz). Belts: 3.2-4.0 mm (8-10 oz). Holsters: 2.4-3.2 mm (6-8 oz). Watch straps: 1.0-1.6 mm (2.5-4 oz). Tooling/carving leather: 2.0-3.2 mm (5-8 oz). Shoes: 1.4-2.0 mm (3.5-5 oz). This calculator includes quick presets for all common project types.
Is leather thickness the same across a whole hide?
No. Leather varies in thickness across a single hide. The back (bend) is the thickest and most consistent area. The belly and flanks are thinner and stretchier. The shoulder is thick but can be uneven. Most quality leather suppliers specify thickness as a range (e.g. 4-5 oz) to account for this natural variation. For consistent results, measure your actual leather before cutting.
What is the difference between iron and chrome-tanned leather thickness?
Vegetable-tanned (veg-tan) leather is firmer and more consistent in thickness, making gauge measurements more reliable. Chrome-tanned leather is softer and more compressible, so a caliper may read slightly thinner under pressure. When converting chrome-tanned leather, measure with light pressure and consider going 0.5 oz heavier than the measured weight for pattern selection.
Sources and References
- Tandy Leather, "Understanding Leather Weights and Thicknesses", 2024
- The Leather Working Group (LWG), "Leather Measurement Standards", 2023
- Springfield Leather Company, "Leather Weight & Thickness Guide", 2024