What Does 20/16 Mean on a Watch Strap?
You've learned to read 75/125 — the length of each strap piece.
But there's another code you'll see on almost every watch strap listing: 20/18. 20/16. 22/18.
Most people scroll straight past it.
Those two numbers quietly determine how your watch looks, how the strap sits on your wrist, and even which buckle you need.
What Does 20/16 Mean on a Watch Strap?
The two numbers describe the strap width at each end.
- First number: width at the lugs, where the strap meets your watch case
- Second number: width at the buckle
So:
20/16 = 20mm at the watch case, tapering to 16mm at the buckle.
Likewise:
20/18 = 20mm at the lugs, tapering to 18mm at the buckle.
A straight strap may be listed as 20/20, or simply as a 20mm watch strap.
The first number must match your watch's lug width. The second is where style and proportion come into play.
HMS Tip 💡
Always check both numbers before ordering. Lug width tells you whether the strap fits your watch; taper tells you how the strap looks and feels once it's on your wrist.
20/18 vs 20/16: What's the Difference?
The difference is only 2mm — but visually, it can make a surprisingly big difference.
20/18 — Subtle Taper
A 20/18 strap narrows by just 2mm.
The result is balanced and understated, making it a versatile choice for everyday watches and modern classics.
20/16 — Stronger Taper
A 20/16 strap narrows by 4mm.
This creates a more pronounced vintage character, particularly suited to traditional dress watches and watches inspired by mid-century designs.
The same principle applies across other sizes:
- 22/18
- 20/16
- 19/16
- 18/16
The lug width may be the same, but the character of the watch can feel completely different.
How Taper Changes the Look of Your Watch
Taper isn't just about measurements.
A tapered strap naturally concentrates visual weight around the watch case. As the strap narrows toward the buckle, the eye is drawn back towards the watch dial.
This can make the watch head feel more prominent while creating a cleaner, slimmer appearance around the wrist.
There's also a practical benefit.
A narrower buckle end creates less bulk underneath a shirt cuff, which is one reason stronger tapering has traditionally been associated with dress watches.
It's similar to good tailoring: the proportions are subtle, but you notice when they're right.
Don't Forget the Buckle Size
The second number also tells you something important about the buckle.
A 20/16 strap normally requires a 16mm buckle.
A 20/18 strap normally requires an 18mm buckle.
So if you're planning to reuse the buckle from an existing strap, don't assume it will fit.
For example, the buckle from a 20/18 strap isn't automatically compatible with a 20/16 strap.
HMS Tip 💡
If you're buying a replacement strap and want to keep your existing buckle, check the buckle width before ordering.
Why Is a Tapered Strap Harder to Make?
A straight strap looks simple because the two edges run almost parallel.
A tapered strap requires much more precise construction.
The leather needs to narrow consistently from the lug end towards the buckle, while the stitching, edge finishing and proportions need to remain symmetrical.
Both sides of the strap also need to taper consistently.
A small difference can become surprisingly obvious once the strap is fitted to a watch.
That's why a clean, well-executed taper is one of those details you may not consciously notice — but you notice immediately when it's wrong.
Which Taper Should You Choose?
There isn't one taper that's right for every watch.
As a general guide:
Slim dress watch → 20/16
A stronger taper complements classic proportions and vintage-inspired dress watches.
Everyday classic watch → 20/18
A moderate taper offers a versatile balance between dressy and casual.
Sport or tool watch → 20/20 or minimal taper
A straighter profile generally suits watches where robustness and function are more important than formal proportions.
And when you're unsure, 2mm of taper is a safe starting point for many classic watch styles.
Check Your Lug Width First
Before choosing a taper, you need to know your watch's lug width.
The first number in 20/16 or 20/18 must match the distance between your watch's lugs.
If you're not sure what your lug width is, see our guide:
Lug Width 101: The One Measurement You Need Before Buying a New Strap
Once you've confirmed the lug width, you can start choosing the taper that best suits your watch.
The Final Rule
Two numbers.
One slash.
A lot more information than it looks.
20/16 tells you the strap starts at 20mm and narrows to 16mm.
20/18 gives you the same 20mm lug width with a more subtle taper.
The first number makes the strap fit your watch.
The second helps define its character.
And that small difference can completely change the way a watch feels on the wrist.
The best details are the ones you learn to see.
Explore More Watch Strap Guides
- Lug Width 101 — How to measure your watch's lug width
- M vs L — How to measure your wrist and choose the right strap size
- Strap Construction 101 — What's inside a leather watch strap
- Strap Anatomy 101 — Learn the names of every part of a watch strap
Find Your Strap
Looking for a strap to match your watch?
Explore the HMS Watch Strap Collection → and find the leather, width and taper that fit your watch and your style.