Grommet Size Chart
Enter the cord, rope or rod diameter, or the hole you already have, to find the grommet size, with the chart in inches and mm.
How to use the grommet size chart
- Choose Grommet type: Plain grommet or Rolled-rim grommet.
- Under I know the, choose Cord, rope or rod diameter, or Hole I already have.
- Type your measurement into Diameter and pick the unit: in, mm or cm.
- In cord mode, check Clearance. It starts at 1 mm and can be set to 0. A 0 setting gives a warning that the cord may bind.
- Read the result rows: Grommet size, Hole to cut (cutter size), Inside diameter and Outside diameter.
- Look at the chart table below the result to see the full list for your chosen type, with the hole, ID and OD in inches and mm.
- If a warning appears, read it before you cut: it may say the cord is too big for the chart, that the clearance is 0, or that no hole matches and name the nearest size.
The four example buttons (5 mm cord, 1/4 in rope, rolled rim, 3/8 in hole and 10 mm rod) fill in the inputs so you can see a result before you enter your own numbers. Copy link keeps all your inputs, Copy result copies the result, and Print / save as PDF prints your inputs, results, steps and the date. Reset clears the form. How it was calculated shows each step with your numbers.
What size grommet do I need for a rope?
Add the clearance to the rope diameter, then pick the smallest grommet whose inside diameter is at least that total. The default clearance is 1 mm, which leaves a little room so the rope can slide through. The tool uses this rule: inside diameter needed = cord + clearance.
For example, an 8 mm cord with 1 mm clearance needs 9 mm. Plain #1 has an ID of 7.29 mm, which is too small. Plain #2 has an ID of 0.362 in, or 9.19 mm, which fits. Its hole to cut is 3/8 in.
The chart has a limit. The largest plain grommet, #4, has an ID of 0.488 in (12.4 mm). A 10 mm rod with 1 mm clearance needs 11 mm. Plain #3 has an ID of 10.998 mm, just short, so #4 is the answer. A cord bigger than the largest size in the chart returns no result, and the tool tells you to look at a maker’s catalogue.
In the rolled-rim list, #2 and #3 both have an ID of 0.430 in, so a cord that fits one is matched to the smaller #2 first. Rolled-rim #4 has the largest ID in the chart, 0.565 in.
What size hole do I cut for a #2 grommet?
For a plain #2 grommet in this chart, cut a hole of 3/8 in (9.53 mm). The hole is the cutter or hole-punch size for that grommet. Fractions are converted by division, so 3/8 in is 0.375 in, and 0.375 × 25.4 = 9.53 mm. A rolled-rim #2 is different: its hole is 7/16 in.
These numbers belong to one maker. Another maker can print a different hole for the same size name: one prints a 13/32 in hole for its #1 rolled-rim grommet, where this chart shows 3/8 in. If you buy a different brand, use its own size sheet.
If you already have a hole, choose Hole I already have. The tool finds the grommet whose cutter hole is within 1/64 in (0.40 mm) of your hole. If none is that close, it warns you, names the nearest size, and names the largest grommet that fits loosely inside your hole.
Sources
Checked October 2026:
- Trican, Grommet Size Chart: plain #00 to #4 and rolled-rim #0 to #4 grommets with hole size, inside and outside diameter in inches
- Stimpson, rolled rim grommets with spur washers: shows that another maker’s rolled-rim sizes differ (for example a 13/32 in hole for its #1)
For estimation; verify critical designs against the applicable standard.
Worked examples
| Input | Result |
|---|---|
| 5 mm cord, 1 mm clearance, Plain grommet | #0 (Plain grommet), hole 1/4 in (6.35 mm), inside diameter 0.248 in (6.3 mm) |
| 0.25 in cord, 0.0625 in clearance, Rolled-rim grommet | #1 (Rolled-rim grommet), hole 3/8 in (9.53 mm), inside diameter 0.38 in (9.65 mm) |
| 0.375 in hole, Plain grommet | #2 (Plain grommet), hole 3/8 in (9.53 mm), inside diameter 0.362 in (9.19 mm) |
| 8 mm cord, 1 mm clearance, Plain grommet | #2 (Plain grommet), hole 3/8 in (9.53 mm), inside diameter 0.362 in (9.19 mm) |
Calculated by the tool above with these values.
Frequently asked questions
What is the inside diameter of a #0 grommet?
A plain #0 grommet has an inside diameter of 0.248 in (6.3 mm) in this chart, and a rolled-rim #0 has 0.270 in (6.86 mm). The 5 mm cord example picks plain #0, since 5 mm plus 1 mm clearance needs 6 mm.
Where can I see grommet sizes in inches and mm?
The chart table shows the hole, inside diameter and outside diameter in both inches and millimetres. Conversion uses 1 inch = 25.4 mm exactly. The finder accepts measurements in in, mm or cm.
What size are rubber, metal or brass grommets?
This chart does not split sizes by material, so it cannot give the size of a specific rubber, metal or brass grommet. Measure the hole you have or read the product’s own size sheet, then use Hole I already have to find the closest size in this chart.
Is there a gromet sizes comparison between makers?
No. This page shows one maker’s table, and it does not compare makers. Other makers use different numbers for the same size name, so treat the chart as a guide and check the maker’s chart before you cut.
Is the calculator free, and is anything I type uploaded?
Yes, the finder is free and needs no sign-up. It runs in your browser, and nothing you type is uploaded. The Copy link button stores your inputs in the link itself.
Related tools
- Heat shrink tubing size chart: pick tubing that fits over a wire or cable.
- O-ring size chart: find the seal size for a groove or fitting.
- Trash bag size chart: match a bag to your bin.
- Mil thickness chart: convert film thickness between mils and other units.
- All calculators: browse every tool on this site.