The only tool you need is a strip of paper. Skip the tape measure, skip the apps. Here is the entire wrist-measurement protocol used at our atelier.
The only tool you need
A strip of paper (any A4 cut at 1cm width works). A pen. A ruler in millimeters. That is the whole kit.
Where to measure
Measure where you actually wear your watch: just above the wrist bone, where the strap usually sits. Not on the bone (too thin), not below it (too thick). Bone, not muscle. Around the wrist, snug but not tight.
When to measure
Mid-afternoon is best. Morning wrists are smaller (less blood flow); evening wrists are slightly larger (more fluid retention). Mid-afternoon is the average.
Reading the number
Wrap the paper around your wrist. Mark where it meets. Lay it flat and measure with a ruler in millimeters. Always millimeters. Inches are imprecise for watch strap sizing — the math is fractional and error-prone.
Wrist size to strap length
| Wrist circumference | Strap size category | POPSTRAP notch (1-8) |
|---|---|---|
| 140-150mm | XS | 1-2 |
| 150-165mm | S | 2-3 |
| 165-180mm | M | 3-5 |
| 180-195mm | L | 5-7 |
| 195-210mm | XL | 7-8 |
Watch case diameter vs wrist width
Old rule: case diameter should be ~50-65% of wrist width. For most wrists between 160-185mm, a 40mm watch is the sweet spot. Smaller wrists may find 40mm bold; larger wrists may find it small.
Flat wrist vs round wrist
Two wrists with the same circumference can feel completely different on the same strap. Flat wrists (more oval cross-section) carry watches wider; round wrists carry them more cleanly. Add 2mm of perceived fit for flat wrists.
The two-finger rule is wrong
Conventional wisdom: "slip two fingers between strap and wrist for the right fit." Actually too loose. The strap should allow one finger, snug. Two fingers and you will have lateral wobble.
Common sizing mistakes
- Measuring over a sweater — always bare skin
- Measuring after exercise — wrist is engorged
- Adding "comfort" mm — the buckle adjustment already handles that
- Trusting cm not mm — 0.5cm is 5mm of error
- Ignoring wrist profile — flat vs round matters
Full POPSTRAP size guide • Shop Drop 01 • Full buying guide.