Good fit
Centred buckle, middle hole, tucked tail
The buckle sits mid-wrist, the pin is in one of the middle holes, and the tail ends just past the second keeper.
Find your fit in a minute
Watch Strap Size Guide
Every Cernir strap is made to order in the length you choose. Two measurements decide it: your wrist and your watch's lug-to-lug. This guide helps you get both right, then turns them into an exact Long End and Short End.
- 5 mmlength steps
- 7 holes6 mm apart
- S · M · Lor a custom length
Strap size calculator
Enter your wrist and your watch's lug-to-lug. A longer watch covers more of your wrist, so it needs less strap. That's why we ask for both.
Strap size calculator
Enter your wrist circumference and your watch’s lug-to-lug measurement. We’ll use both to recommend a strap length for a balanced fit.
cm
Measure snugly at the spot where you wear your watch.
mm
Measure from one outer lug tip to the opposite outer lug tip—not the case diameter.
Lengths exclude the watch case and buckle hardware. Handcrafted straps may vary slightly within our production tolerance.
How to measure
Two measurements, one minute. All you need is a soft tape measure, or a strip of paper and a ruler.
-
1Measure your wrist
Wrap a soft tape measure around your wrist where your watch sits, on the arm side of the wrist bone. Keep it flat and snug, without pressing into the skin, and read the number where the tape overlaps.
No tape? Wrap a strip of paper, mark the overlap, then lay it flat on a ruler. Paper is more reliable than string, which can stretch.
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2Measure lug-to-lug
Lay the watch face up. Measure in a straight line along the 12 to 6 o'clock axis, from the tip of the top lugs to the tip of the bottom lugs, in millimetres or inches.
Not the case diameter, which runs across the case. With curved lugs, measure the straight line seen from above, not along the curve.
-
3Or measure a strap that fits
Lay each end of a two-piece strap flat. Measure the Long End from the spring-bar end to the tip, and the Short End from the spring-bar end to the buckle, leaving the buckle out.
Watch strap size chart
Find your wrist on the left and your watch's lug-to-lug across the top. Each cell is the Long End / Short End in millimetres, made to order in 5 mm steps.
S
105 / 65 mmTotal 170 mmWrist 15.4–16.4 cm · 6.1–6.5 in*
M
115 / 75 mmTotal 190 mmWrist 17.4–18.4 cm · 6.9–7.2 in*
L
125 / 85 mmTotal 210 mmWrist 19.4–20.4 cm · 7.6–8.0 in*
| Wrist | Lug-to-lug40 mm | Lug-to-lug44 mm | Lug-to-lug48 mm | Lug-to-lug52 mm |
|---|---|---|---|---|
| 14.0 cm5.5 in | 100 / 60 | 95 / 55 | 95 / 55 | 90 / 50 |
| 14.5 cm5.7 in | 100 / 60 | 100 / 60 | 95 / 55 | 95 / 55 |
| 15.0 cm5.9 in | 105 / 65S | 100 / 60 | 100 / 60 | 95 / 55 |
| 15.5 cm6.1 in | 105 / 65S | 105 / 65S | 100 / 60 | 100 / 60 |
| 16.0 cm6.3 in | 105 / 65S | 105 / 65S | 105 / 65S | 100 / 60 |
| 16.5 cm6.5 in | 110 / 70 | 110 / 70 | 105 / 65S | 105 / 65S |
| 17.0 cm6.7 in | 115 / 75M | 110 / 70 | 110 / 70 | 105 / 65S |
| 17.5 cm6.9 in | 115 / 75M | 115 / 75M | 110 / 70 | 110 / 70 |
| 18.0 cm7.1 in | 115 / 75M | 115 / 75M | 115 / 75M | 110 / 70 |
| 18.5 cm7.3 in | 120 / 80 | 120 / 80 | 115 / 75M | 115 / 75M |
| 19.0 cm7.5 in | 125 / 85L | 120 / 80 | 120 / 80 | 115 / 75M |
| 19.5 cm7.7 in | 125 / 85L | 125 / 85L | 120 / 80 | 120 / 80 |
| 20.0 cm7.9 in | 125 / 85L | 125 / 85L | 125 / 85L | 120 / 80 |
| 20.5 cm8.1 in | 130 / 90 | 130 / 90 | 125 / 85L | 125 / 85L |
| 21.0 cm8.3 in | 135 / 95 | 130 / 90 | 130 / 90 | 125 / 85L |
* With a 44 mm lug-to-lug watch. The wrist ranges move with your watch, and wrists in between get a custom length such as 110/70 or 120/80 mm.
How strap sizes are written
A size like 115/75 is simply the Long End and the Short End in millimetres. Here is the full anatomy.
- ALug width must match the gap between your watch's lugs. Find your lug width
- BBuckle width is the width of the Short End where it meets the buckle. A tapered strap narrows from A to B, for example 20 to 18 mm.
- CLong End has the holes. It sets how much tail you have after fastening.
- DShort End carries the buckle. It sets where the buckle sits under your wrist.
- EHoles: seven, 6 mm apart. When the length is right, the pin rests in the middle one.
- FKeepers: two loops on the Short End that hold the tail flat.
| S | M | L | |
|---|---|---|---|
| C · Long End | 105 mm | 115 mm | 125 mm |
| D · Short End | 65 mm | 75 mm | 85 mm |
| Total | 170 mm | 190 mm | 210 mm |
| E · Holes | 7 holes, 6 mm apart | ||
How the calculator finds your length
No guesswork and no wide size bands: one formula, rounded to the lengths we actually make.
Total length=wrist−lug-to-lug+55 mm
Example: 17 cm wrist, 47 mm watch: 170 − 47 + 55 = 178 mm → 110 / 70 mm
- 1
Subtract the watch
The watch head covers part of your wrist, so its lug-to-lug comes off your wrist size.
- 2
Add 55 mm for the fit
The strap that passes through the buckle and both keepers, with the pin in the middle hole.
- 3
Split and round
The Long End is 40 mm longer than the Short End, both rounded to the nearest 5 mm.
- 4
Room to adjust
Seven holes, 6 mm apart, give about 18 mm either way from the middle hole.
Results outside Long End 80–160 mm or Short End 40–100 mm are confirmed by our team before production.
What a well-fitted strap looks like
Seen from the underside of the wrist. Use this to check the fit when your strap arrives.
Too short
Last hole, tail barely reaches the keepers
The buckle is pulled away from the centre. Choose a longer length.
Too long
First hole, tail runs past the keepers
The buckle sits off centre and the tail lifts away. Choose a shorter length.
Good to know
A few situations where a little extra care helps.
Between sizes
Trust the calculator. It already picks the nearest 5 mm, and the holes cover the rest.
Curved lugs
Measure lug-to-lug in a straight line, tip to tip, not along the curve.
Thick watches
Around 14 mm thick or more? Ask us whether to go one step longer.
Butterfly clasp
Use the same result. The lengths are the same as for a pin buckle.
Small or large wrists
If the calculator asks for a manual check, send us your numbers.
Sizing questions, answered
The questions we hear most from customers choosing a length.
How do I measure my wrist for a watch strap?
Wrap a soft tape measure around your wrist where you wear your watch, on the arm side of the wrist bone. Keep it flat and snug without pressing into the skin, then read the number where the tape overlaps. Don't add any extra for comfort: the calculator already allows for it.
How can I measure my wrist without a tape measure?
Wrap a strip of paper around your wrist, mark where it overlaps, then lay it flat and measure up to the mark with a ruler. Paper works better than string, which can stretch and give a smaller number.
What is lug-to-lug, and why does it change my strap length?
Lug-to-lug is the straight-line distance from the tip of the top lugs to the tip of the bottom lugs. The watch head covers that part of your wrist, so a longer watch needs less strap than a shorter one on the same wrist. It is not the case diameter: most watches measure several millimetres more lug to lug.
What do strap sizes like 115/75 mean?
The first number is the Long End (the side with the holes) and the second is the Short End (the buckle side), both in millimetres. Neither includes the buckle or the watch. Some brands write the Short End first, so check which is which when you compare.
What size strap do I need for a 7-inch wrist?
A 7-inch wrist is about 17.8 cm. With a watch up to 48 mm lug to lug, the calculator recommends size M (115/75 mm). From 49 mm lug to lug, it recommends 110/70 mm.
What if I'm between two sizes?
Go with the calculator result. It already picks the nearest length in 5 mm steps, and the seven holes, 6 mm apart, give you about 3.6 cm of adjustment around the middle hole.
Is strap length the same as lug width?
No. Lug width is the width of the strap where it meets the watch, measured between the lugs. Length is how long each end is. We make straps in any lug width, odd and half sizes included, with buckle widths from 10 to 24 mm. See our lug width guide.
Does the same size work with a butterfly clasp?
Yes. Our butterfly clasp straps use the same Long End and Short End lengths, so use the calculator result as it is.
Will a leather strap stretch over time?
Leather softens and shapes to your wrist, but the finished length changes very little. Choose the length that fits now rather than a shorter one in the hope it stretches.
How long should the tail be?
With the pin in the middle hole, the tail should pass through both keepers and finish just beyond the second one. If it barely reaches the first keeper, the strap is too short; if it runs well past the second, it is too long.
Can I order a length other than S, M or L?
Yes. The calculator suggests a custom Long End / Short End pair in 5 mm steps, and every strap can be made to your own measurements. If you already own a strap that fits, measure its two ends without the buckle and order those lengths.
What if the calculator asks for a manual sizing check?
Your measurements may still be fine. It means the result falls outside the lengths we can make through the website, so our team will confirm it with you before production.
What if my strap doesn't fit?
Contact us at support@cernir.com with your wrist and lug-to-lug measurements and we'll review the fit with you. Returns follow our Return & Refund Policy. Custom lengths can carry a restocking fee, so if you're unsure, ask us to check your size before you order.
Beyond S, M and L
Any length, made to measure
Our standard sizes fit most wrists, but they are not the limit. Every Cernir strap is handcrafted to order, so we can make the Long End and Short End to the length you need, in 5 mm steps.
Not sure? Send us these
- Your wrist size, in cm or inches
- Your watch model, or its lug-to-lug in mm
- A photo of the watch on your wrist, if you can
Email support@cernir.com or use live chat, and we'll reply with the length to order.