If you want to replace the strap on a watch, one measurement matters before almost anything else:
lug width.
Searches such as “watch lug width explained,” “what is lug width on a watch,” “how to measure watch strap size,” and “20mm vs 22mm watch strap” are common because buying the wrong strap width can prevent the strap from fitting correctly.
What Is Watch Lug Width?
Lug width is the distance between the inside surfaces of the watch lugs.
This is where the strap or bracelet connects to the case.
It is normally measured in millimeters.
Common Watch Lug Widths
Typical sizes include:
- 18mm
- 20mm
- 21mm
- 22mm
- 24mm
Other sizes also exist.
Why Is Lug Width Important?
The replacement strap needs to fit the space between the lugs.
If the strap is too wide, it may not fit.
If it is too narrow, visible gaps and unwanted movement may result.
How Do You Measure Lug Width?
Measure the inside distance from one lug to the other.
A ruler can work, but calipers provide greater precision.
Measure the space where the spring bar sits rather than the outside width of the case.
Is Lug Width the Same as Strap Width?
At the case attachment point, yes.
A watch with 20mm lug width generally requires a strap that measures approximately 20mm at the lugs.
However, the strap may taper toward the buckle.
What Is Strap Taper?
Strap taper describes how the strap becomes narrower as it moves away from the case.
For example:
20mm → 16mm
means the strap begins at 20mm at the lugs and narrows toward approximately 16mm at the buckle.
20mm vs 22mm Watch Strap
A 22mm strap is visibly broader and may give the watch a more substantial appearance.
A 20mm strap can look more refined depending on the case.
Neither size is inherently better.
Can You Put a 22mm Strap on 20mm Lugs?
Generally, you should use the correct strap width.
Forcing an oversized strap between smaller lugs can:
- deform the strap
- create poor fit
- make installation difficult
Can You Put a 20mm Strap on 22mm Lugs?
It may physically attach in some cases, but visible gaps will remain.
The strap can also move laterally more than intended.
Using the correct width is preferable.
Does Lug Width Affect Watch Appearance?
Yes.
A narrow strap can make a case appear larger.
A broader strap can create a more substantial and sporty look.
Case diameter and strap width should feel visually balanced.
What Lug Width Is Good for a 40mm Watch?
There is no universal answer.
Many 40mm watches use approximately 20mm or 22mm lug widths.
Case shape and design determine the most appropriate proportion.
What Lug Width Is Good for a 38mm Watch?
A 38mm watch may commonly use widths such as:
- 18mm
- 19mm
- 20mm
Again, there is no strict rule.
Why Do Some Watches Use Odd Lug Widths?
Widths such as 19mm or 21mm may be chosen for specific case proportions.
The downside is that replacement strap availability may be more limited than with common even-numbered sizes.
Integrated Bracelets and Lug Width
Some integrated-bracelet watches do not use conventional open lugs.
These watches may require straps specifically designed for the case.
A generic 20mm or 22mm strap may not fit even if the nominal width appears correct.
Lug Width vs Lug-to-Lug
These are completely different measurements.
Lug Width
Measures the horizontal gap between the lugs where the strap attaches.
Lug-to-Lug
Measures the length of the case from the top lug to the bottom lug.
Both are important, but for different reasons.
Lug Width and Spring Bars
Spring bars must also match the watch's attachment system.
Correct strap width does not automatically guarantee that every spring bar will fit.
Quick-Release Straps
Many modern straps include quick-release spring bars.
You still need the correct lug width.
For example, a 20mm quick-release strap is intended for compatible 20mm lug spacing.
How to Choose a Replacement Watch Strap
Before ordering, check:
- lug width
- buckle width
- strap length
- spring-bar compatibility
- case design
- strap thickness
Specht & Sohne Strap Sizing
Different Specht & Sohne models may use different lug or bracelet configurations.
Check the individual model dimensions before ordering a replacement strap.
Final Thoughts
So, what is watch lug width?
It is the distance between the inside edges of the lugs where the strap attaches.
If your watch has a 20mm lug width, start by looking for a compatible 20mm strap.
Correct sizing improves:
fit + security + appearance + comfort.