Watch Strap Size Guide: How to Find the Right Lug Width for Any Watch

The most common mistake when ordering a watch strap is ordering the wrong size. Lug width is not a preference — it's a measurement, and it must match your watch exactly. This guide shows you three ways to find your lug width, a reference table for common watches, and what to do if yours isn't listed. 

What Is Lug Width?

Lug width is the internal distance between the two lugs on your watch case — the gap the spring bar spans. It's always a whole number in millimetres. The most common sizes are 18mm, 19mm, 20mm, 21mm, 22mm, and 24mm.

A strap with a lug width of 20mm will seat exactly on a watch with 20mm lugs. A 21mm strap will not fit, and a 19mm strap will leave visible gaps and may allow the spring bar to come loose.

Lug width is the most important measurement when ordering any watch strap. Get this right first — everything else (length, taper, leather) is secondary.

Three Ways to Find Your Lug Width

Method 1: Look It Up (Fastest)

Search "[your watch brand and model] lug width" — manufacturer specification sheets, watchmaker databases (WatchBase, Chrono24 listing specs), and collector forums will have the answer for almost any reference made in the last 50 years. This takes under two minutes and is the most reliable method for current production watches.

Method 2: Measure Directly (Most Accurate for Vintage)

Use a digital caliper — available inexpensively online or at hardware stores. Place the jaws inside the gap between the two lugs and read the measurement. For curved or angled lugs, measure at the widest point of the gap. The result should be a whole number in millimetres; if you get 19.8mm, round to 20mm.

No caliper? A millimetre ruler held carefully across the inside of the lug gap can give a rough reading. Less precise than a caliper but usually sufficient for standard lug widths.

Method 3: Check Your Existing Strap (If It Fits Correctly)

If you have a strap that currently fits your watch well, measure its lug end width. This is the most common approach when the original strap is still in place.

Lug Width Reference Table

Common lug widths by watch brand and model. Note that some models exist in multiple case sizes with different lug widths — always verify your specific reference number.

What If My Lug Width Isn't Listed?

If your watch isn't in the table above, three options:

• Measure directly: A digital caliper is definitive. Most watches fit neatly into 1mm increments — if your measurement is fractional, round to the nearest whole number.

• Contact JackCoHenry: Send us your exact watch brand, model, and reference number. We maintain an extended reference database and can confirm your lug width before you order.

• Check WatchBase or Chrono24: Both platforms list lug width in technical specifications for tens of thousands of watch references.

What About Strap Length?

Lug width tells you which strap fits your watch. Strap length tells you which size fits your wrist. These are separate measurements — see the full sizing guide for length calculations.

→  Watch Strap Sizing Guide

Frequently Asked Questions

Q. Can I use a strap that is 1mm wider or narrower than my lug width?

No. The spring bar must seat inside the lug holes on both sides. A strap that is 1mm too wide will not fit between the lugs; a strap that is 1mm too narrow will leave visible gaps and the spring bar may not hold securely.

Q. My watch has a curved lug — does that affect the strap width?

No. Lug width (the gap between the lugs) is independent of lug shape (whether they curve downward or sit flat). However, curved lugs do affect whether you need a straight-end or curved-end strap. See the Fit Guide for details.

Q. I have an integrated strap (Audemars Piguet Royal Oak, Cartier Santos) — does this apply?

No. Integrated strap systems use a proprietary insert that attaches differently from a standard spring bar. Standard aftermarket straps are not compatible with integrated strap watches without the original insert.

Q. What is the most common lug width?

20mm. It covers the majority of popular sport and dress watches from Rolex, Omega, IWC, and most other major manufacturers. If you're buying a first strap without having measured yet and you own one of these brands, 20mm is the most likely correct size — but always verify before ordering.

Q. Do lug widths change between different case sizes of the same watch?

Sometimes. A watch available in 36mm and 41mm case sizes may use different lug widths at each size. Always check by the specific case size and reference number, not just the model name.

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→  Best 20mm Leather Watch Straps (2026)

→  Best 22mm Leather Watch Straps (2026)

→  Best 24mm Leather Watch Straps (2026)

→  Watch Strap Sizing Guide

→  Fit Guide — will this strap fit my watch?