Watch glass thickness – how to choose the right size?

Two glasses can have exactly the same diameter but differ in thickness. For example, a glass with a diameter of 30.4 mm can come in versions of 1.0 mm, 1.5 mm, 2.0 mm, or even thicker.

Each of these variants is a different product and should not be treated as automatically interchangeable.

Why is glass thickness important?

Thickness affects, among other things:

• the way the glass is seated in the case,
• the height of the glass relative to the bezel,
• the amount of space above the hands,
• the interaction with the glass seal,
• the appearance of the watch after assembly.

Therefore, when replacing glass, it is necessary to replicate not only its diameter but also the correct thickness and profile.

Glass 1.0 mm – when is it used?

Glasses with a thickness of 1.0 mm are relatively thin and are found in many watches where the case design allows for a small glass height.

The Kurant store offers a wide range of flat mineral glasses of 1.0 mm in various diameters. :contentReference[oaicite:1]{index=1}

See flat mineral glasses 1.0 mm

Glass 2.0 mm – how does it differ from 1.0 mm?

A glass with a thickness of 2.0 mm is twice as thick as a 1.0 mm glass. At the same diameter, it will therefore sit differently in the case and may protrude higher above its surface.

Your site features separate products and series of 2.0 mm glasses, e.g., flat mineral glass 22.4 mm × 2.0 mm. :contentReference[oaicite:2]{index=2}

Is thicker glass always better?

No. Thickness should not be chosen based on the principle of "the thicker, the better".

The most important factor is matching the watch's construction. Too thick glass can:

• protrude too much above the case,
• not fit the bezel,
• change the watch's appearance,
• make proper seating difficult.

On the other hand, glass that is too thin may sit too low or not correspond to the original construction.

Can 1.0 mm glass be replaced with 1.5 mm glass?

It should not be assumed that such a replacement will be correct just because the diameter is identical.

Before changing the thickness, it is necessary to check:

• the depth of the glass seat,
• the method of attachment,
• the height of the bezel,
• the distance from the hands,
• the type of seal.

The safest option is to use a thickness that corresponds to the original glass.

How to measure the thickness of old glass?

The glass must first be removed from the watch.

The thickness is best measured with calipers at the point that corresponds to the construction of the given glass.

For flat glass, the measurement is relatively simple – we measure its total thickness.

How to measure the thickness of spherical glass?

With convex glass, it is important to remember that the center is higher than the edge.

Therefore, the total height of the glass should not be automatically interpreted as the thickness of its edge.

When selecting, the profile should be compared with the original glass, not just one value.

How to measure lens glass?

In the case of lens glass, there are two important dimensions:

• thickness at the edge,
• thickness in the center.

An example designation:

3.5 × 1.5 mm

means a glass whose center is about 3.5 mm, while the edge is about 1.5 mm.

Thus, such glass cannot be compared to regular flat glass of 1.5 mm and considered the same.

See: what is the difference between flat, spherical, and lens glass

Glass thickness and hands

The profile and thickness of the glass affect the amount of space above the dial and hands.

In a watch where the hands are positioned high, using too low a profile may result in insufficient space.

Therefore, in some designs, convex or lens glasses are factory-fitted instead of flat ones.

Glass thickness and bezel

In many cases, the glass should be at a specific height relative to the bezel.

Too thick glass may protrude more than the original, while too thin glass may sit too deep.

This has both aesthetic and structural significance.

Glass thickness and I-ring seal

For glass mounted on a seal, the height of the I-ring must also be taken into account.

Thus, the thickness of the glass cannot be selected independently of how it is seated.

The entire system should be analyzed as:

case + seal + glass.

See: how to select an I-ring for watch glass

Same diameter, different thickness – example

Let's assume that a glass with a diameter of 30.4 mm is needed.

The catalog may include:

• 30.4 × 1.0 mm,
• 30.4 × 1.5 mm,
• 30.4 × 2.0 mm.

All have a diameter of 30.4 mm, but they are three different parts.

Therefore, simply stating the diameter 304 is not enough to place an order.

See: what does the glass size 304 mean

Does the glass material matter when it comes to thickness?

Yes. Plexiglass, mineral glass, and sapphire have different properties, and the watch's construction may be adapted to a specific material and profile.

Therefore, mineral glass of 1.5 mm and sapphire glass of 1.5 mm should not be considered interchangeable solely based on identical diameter and thickness.

See: plexiglass, mineral or sapphire – which glass to choose?

How to select thickness when the old glass is broken?

If it is not possible to measure the old glass, it is necessary to determine the construction of the seat in the case and the method of installation.

Helpful may be:

• a preserved fragment of glass,
• the height of the bezel,
• the depth of the seat,
• the old seal,
• the documentation for the specific watch model.

The diameter of the seat alone does not determine the correct thickness of the glass.

How to select glass thickness step by step?

1. Remove the old glass from the watch.
2. Measure the diameter.
3. Measure the thickness of the glass.
4. Identify the profile: flat, spherical, or lens.
5. Check the method of attachment.
6. If there is an I-ring, consider its height and thickness.
7. Compare the new part with the original glass before installation.

Watch glasses in various thicknesses at Kurant Wholesale

The watchmaking wholesaler Kurant has in stock over 80,000 pieces of watch glasses in many diameters, thicknesses, materials, and profiles.

For example, flat mineral glasses are available in separate series by thickness, making it easier to select the appropriate version for the case. :contentReference[oaicite:3]{index=3}

See watch glasses at Kurant Wholesale

Also see: how to select glass for a watch – complete guide