Measuring lug width: the millimetre figure between the lugs
Before you can change your watch strap, you need the right width. What is measured is the distance between the two lugs, that is the small horns on the case that the strap fits into. Take a ruler or a calliper and read off the inner distance in millimetres, at the point where the spring bar sits.
This value, the so-called lug width, is almost always an even number on watches. As a rough rule of thumb, women's watches are often between 12 and 16 millimetres, classic men's watches mostly 18 to 22 millimetres, and sturdy dive or sports watches often 20 to 24 millimetres. These ranges are only a guide; you should always measure the specific watch, because even a one-millimetre deviation results in a strap that either jams or wobbles.
The length of the spring bar is also important, not just the width of the strap. The bar must fit exactly into the holes of the lugs, otherwise it will not hold securely. It is best to note down the measured figure, so that you find the right size straight away when buying a replacement strap.
If you do not want to measure the width of your specific watch yourself, a look at the data sheet or the manufacturer's page for the model often helps. For many watches the lug width is given there directly. If in doubt, though, rely on your own measurement, because the figure can differ, especially on older or modified watches.
The spring bar tool: understanding the fork end and the tip end
The most important tool for the change is the spring bar remover, or spring bar tool for short. It has two different working heads at its two ends, and anyone who knows the difference works much more safely. One side is a small fork, the other a fine tip.
You push the fork end in from the outside between the strap and the lug. The fork grips the shoulder of the spring bar and compresses it; this works with almost all leather straps and open constructions. You need the tip end when the lug has a hole on the side, a so-called through-hole, through which you can press the bar in directly.
A solid tool has hardened, cleanly finished ends that do not bend straight away. Cheap versions made of soft metal bend under pressure and then slip off more easily. You can find which spring bar tools and replacement bars are worthwhile in our Tools and Care category, which also lists what to look for in terms of build quality.
For delicate watches with polished lugs there are spring bar tools with interchangeable tips, some made of plastic, which are gentler on the metal. Anyone who changes straps more often also likes to choose models with a spring-loaded blade, which makes slipping off harder. For occasional changes, however, a solid standard tool is perfectly sufficient; what matters most is the clean finish of the ends.
Changing a watch strap step by step
The change itself is no magic if you work calmly and in the right order. Take a clean, well-lit surface and lay a soft cloth underneath to protect the case and crystal. Keep a small container ready so that a spring bar that pops out is not lost.
- Compress the spring bar: Place the fork of the tool between the strap and the lug, grip the shoulder of the spring bar and press it together towards the centre of the strap. For watches with a hole, push the tip into the hole from the side instead.
- Release the old strap: As soon as one end of the bar is free, carefully tilt the strap out. Repeat the process on the other side, and the old strap will be completely in front of you.
- Fit the new strap: Pass the spring bar through the loop of the new strap. First hook one end of the bar into one hole of the lug, then tension the other end with the tool and let it slide into the opposite hole.
- Check it has clicked in: Then pull lightly on the strap and wiggle it gently. If it sits firmly and cannot be pulled off, the bar has clicked in properly. This check pull is exactly what decides whether the watch later falls off your wrist or not.
Take your time deliberately for the first few changes and practise on a cheaper watch. With a bit of routine, a complete strap change takes only a few minutes. The check pull at the end is the step you should never skip.
Quick-release spring bars with quick release as a convenient alternative
Many modern straps now have quick-release spring bars, often called quick release. These bars have a tiny lever, a small metal tab, that you pull aside with your fingernail. This retracts the bar a little, and the strap comes off without any tool.
The advantage is obvious: you can swap the strap in seconds without touching the delicate lugs, and the risk of a scratch drops noticeably. Anyone who switches between leather, rubber and a pass-through strap depending on the occasion saves a lot of time this way. When buying a replacement strap, simply make sure it comes with quick-release bars in the lug width you measured.
A note on safety: even with quick release, check after every change with the light pull that the bar has really fully disengaged. The convenience tempts you to become sloppy, but a lever that has only half clicked in does not hold reliably. Two seconds of checking saves you a dropped watch.
Materials compared: leather, metal, rubber, NATO
Which tool you need and how involved the change is depends heavily on the strap type. A leather strap is the easiest, a screwed metal bracelet the most demanding. The overview below sorts the common materials by attachment and the tool required.
| Material | Attachment | Tools | Effort |
|---|---|---|---|
| Leather | Spring bar, often with quick-release | Spring bar tool or none at all | low |
| Rubber | Spring bar, often quick-release | Spring bar tool or none at all | low |
| NATO / pass-through strap | Strap is threaded under the bars | none, spring bars stay fitted | very low |
| Metal with pins | Spring bar plus pins in the link bracelet | Spring bar tool, pin pusher for shortening | mid-range |
| Metal with screws | screwed links and end links | precisely fitting screwdriver | high |
How often a change is needed at all depends heavily on the material. Leather straps wear out fastest through skin contact and sweat and become hard or cracked over time, while rubber and metal last for many years. A new strap is therefore the simplest and cheapest way to give a frequently worn watch a fresh look again.
The NATO or pass-through strap is a special case because you do not remove anything at all. The strap is simply threaded under both fitted spring bars, which is particularly secure because the watch still holds even if a bar breaks. A metal bracelet with pins, in turn, can be adjusted in length on the wrist with a pin pusher, while screwed links require the matching screwdriver. Where best to store the individual straps and watches is shown in our overview of watch boxes, and for travel the compact travel cases are a good fit.
Common mistakes and when to go to the jeweller
Most damage during a strap change is caused not by a lack of skill but by haste. Three mistakes come up again and again, and all three are easy to avoid. If you know them, you work more cleanly from the start.
First, scratched lugs: they occur when the tool's blade slips and runs across the case. Second, the bent spring bar, which happens when you push with too much force or at the wrong angle instead of compressing the bar cleanly. Third, the wrong width, when the strap was only measured roughly and ends up jamming or wobbling. The same approach helps against all three: work slowly, with a cloth underneath, with proper tools and with the bar width measured exactly beforehand.
There are situations in which a trip to the jeweller or watchmaker is the smarter decision. Screwed metal bracelets with tiny screws, firmly screwed end links, and valuable or water-resistant watches, where a scratch would be really expensive, belong in experienced hands. That is not an admission of incompetence but simply the cheaper calculation if you care about the watch.
One point many people overlook: the strap change itself does not affect the watch's water resistance, because the lugs lie outside the case. If the crown was pulled by accident or the case was opened while handling it, however, the situation is different. For water-resistant watches, a water resistance check at a workshop is worthwhile after any heavier work on the case, before the watch goes back into the water.
If you are working on the watch anyway afterwards, it is worth a look at related care topics: how to deal with small scratches in the plastic crystal yourself is explained in the article Polishing acrylic glass, and why an automatic should stay fully wound in between is covered under Power reserve explained. If you want to expand your tools, you will once again find what you need in our category Tools and care. Watch knowledge from TopWatchReviews collects even more basics about the watch itself.