Grommet Size Number to Hole Diameter Converter
Convert grommet and eyelet size numbers to hole diameter in inches and millimeters.
Covers standard brass, stainless steel, and spur grommets.
Select a grommet size number — see the hole diameter and details.
Grommets and eyelets are metal rings inserted into holes in fabric, canvas, leather, or other sheet materials to reinforce the hole and prevent tearing. The size number system assigns a sequential number to each standard hole diameter, but the numbering is not intuitive — you need a conversion table to know the actual dimensions.
Grommet vs eyelet terminology: A grommet consists of two parts: a barrel (the ring with a tube that passes through the hole) and a washer (a flat ring that clinches onto the back). An eyelet is typically a single-piece ring that rolls or flares over on the back side. In practice, the terms are often used interchangeably, though true grommets (two-piece) provide a stronger, more finished installation.
Standard grommet sizes and their hole diameters:
| Size Number | Hole Diameter (inches) | Hole Diameter (mm) |
|---|---|---|
| 00 | 3/16 (0.1875) | 4.8 |
| 0 | 1/4 (0.250) | 6.4 |
| 1 | 5/16 (0.3125) | 7.9 |
| 2 | 3/8 (0.375) | 9.5 |
| 3 | 7/16 (0.4375) | 11.1 |
| 4 | 1/2 (0.500) | 12.7 |
| 5 | 5/8 (0.625) | 15.9 |
| 6 | 3/4 (0.750) | 19.1 |
| 7 | 7/8 (0.875) | 22.2 |
| 8 | 1 (1.000) | 25.4 |
| 10 | 1-3/8 (1.375) | 34.9 |
| 12 | 1-1/2 (1.500) | 38.1 |
Material options:
- Brass: The most common grommet material. Naturally corrosion-resistant, easy to set, and available in plain (gold-tone) or nickel-plated finishes. Suitable for tarps, banners, shower curtains, and crafts.
- Stainless steel: More expensive but offers superior strength and corrosion resistance. Required for marine applications, outdoor signage in coastal areas, and anywhere exposed to salt water or harsh chemicals.
- Aluminum: Lightweight and corrosion-resistant but softer than brass. Used in lightweight applications and where weight is a concern.
- Plastic/nylon: Non-conductive and corrosion-proof. Used in electrical applications and where metal contact is undesirable.
Self-piercing (spur) grommets: Spur grommets have sharp teeth on the barrel that punch through the material during installation, eliminating the need to pre-cut a hole. They are faster to install but only work on softer materials like fabric, thin leather, and vinyl. For heavier materials like canvas or thick leather, always pre-punch the hole.
Installation tools:
- Hand setting tools: A die set and setter tool used with a hammer. Inexpensive but requires practice to get consistent results.
- Plier-type setters: Squeeze-handle tools for small grommets (sizes 00-2). Good for occasional use and crafts.
- Bench-mounted presses: Lever-operated presses that provide consistent, even pressure. The best choice for production work or large grommets.
- Hole punch: Always punch the hole slightly larger than the grommet barrel to ensure a clean fit. The barrel should slide through without forcing.