The Challenge of Perfect Sizing — And How We’re Getting Closer

The Challenge of Perfect Sizing — And How We’re Getting Closer

Getting the sizing just right has been one of the toughest challenges since day one at Sifu Straps.

After researching what limited data exists on average wrist sizes, we knew a simple “one size fits all” wasn’t going to cut it, especially not with our patented Keeper-First™ design. Instead, we committed to three core sizes: Small, Medium, and Large—each thoughtfully engineered to deliver the cleanest fit possible across a wide range of wrists.

Why Not Just Make One Size?

It’s a fair question. But here’s the issue: due to the way our Keeper-First™ layout is designed, sizing needs to be intentional.

Let’s say someone with a 6" wrist tries to wear our Large strap. Technically, they could not "make it fit," it wouldn’t be a good look, or feel. The 12 and 6 o'clock keepers would be pressing right up against the case, and the strap would hang loose with excess slack.

On the other hand, if you have a 7.5" wrist and wear a Small, the 12 and 6 o’clock keepers would end up under your wrist, defeating the entire design aesthetic. These keepers are meant to sit at the sides of your case—ideally at the 10 and 3 o’clock positions when looking straight down your arm.

What We Based Our Sizing On

To build the most accurate fit, we turned to one of the most comprehensive sources available: the 1988 Anthropometric Survey of U.S. Army Personnel. It included data from 3,982 individuals of mixed gender and ethnicity, offering a strong representative sample of American wrist sizes.  This study found the average male wrist to be 6.86 +/- 0.33” (17.42 +/- 0.83 cm).  The average female wrist was found to be 5.95 +/- 0.27” (15.12 +/- 0.69 cm)

🧭 Understanding Wrist Sizes: Small, Medium, and Large

To make sizing easier to understand, here’s a general breakdown of what’s considered a small, medium, or large wrist for both men and women, based on anthropometric data:

Wrist Size Guide:

This breakdown can help you determine which Sifu Strap size (Small, Medium, or Large) will offer the cleanest fit based on your wrist measurement.

Based on this study, we built three base sizes, and below are our general recommendations.

• Small (for 5.5"–6.5" wrists)

• Medium (for 6.5"–7")

• Large (for 7"+)

But even then, we quickly learned that sizing is incredibly subjective.

Wrist Size Isn’t the Whole Story

Here’s why sizing isn’t a one-variable equation:

1. Wrist fit preference — Do you like your watch snug or loose?

2. Watch head dimensions — A long lug-to-lug case can shift where the strap rests.

3. Spring bar position — How high the watch case sits above the wrist affects keeper positions. 

4. Keeper placement preference — Aesthetics matter. Most people prefer those keepers to be visible, in the 9 or 10 o'clock and 3 or 4 o'clock positions. 

5. Wrist shape — Round or flat?  this makes a noticeable difference in keeper placement.

I wear a watch daily, too tight for 35 years, admittedly. This could be the reason I have both a 6.5" and a 7" wrist, depending on the day. Through wear testing, I found the perfect keeper placement to be 10 and 3 o’clock—symmetrical and balanced when the arm is extended forward.

With that in mind, our Gen 1 sizing placed the keepers at 10 and 3 o’clock on the Small, Medium, and Large for wrists of 5.5", 6.5", and 7.5", respectively.

🤔 What If You Straddle Sizes?

If your wrist measurement falls right between sizes, here’s what we recommend:

• At 6" — Go with a Small. This offers the best balance for most case sizes and keeper alignment.

• At 6.5" — Go with a Medium. This offers the best balance for most case sizes and keeper alignment.

• At 7" — You can wear either Medium or Large, depending on your preference.

  • If you prefer the keepers to sit slightly wider at 10 and 4 o’clock, choose Medium.

  • If you prefer a more traditional placement at 10 and 3 o’clock, go with the Large.

Feedback and Gen 2 Adjustments

After 5 months in the wild, hundreds of straps shipped to over 20 countries, and dozens of reviews and Instagram comments later, we feel good about where we landed.

That said, we did hear some feedback:

• A few 7" wrist customers felt Medium was too short.

• A few 7" wrist customers said Large was too long.

So for Gen 2, we made surgical updates:

• Small and Large sizes increased by 3mm

• Medium size increased by 4mm

• We also standardized the distance between the buckle and middle keeper across all sizes, which centers the buckle more naturally and streamlines our production by eliminating some clamps and templates.

Final Thoughts

We think we got pretty close to a home run on our first swing. But at Sifu, we’re always refining. Sizing will never be a one-size-fits-all formula, but with real-world feedback and real wrist data, we’re constantly pushing to improve.

If you ever have sizing questions, reach out. We’re listening—and improving—with every strap we make.