Metric drill bit sizes
Millimeter diameters only — the labels printed on most imported and European index cases. Each row lists the metric label, decimal inch, and mm so you can match a drawing that specifies diameter in millimeters without hunting the full four-system chart. Need fractional, number, or letter sizes? Use the links below or the full chart.
Full size chart · Size finder · Drill hub · Fractional · Number · Letter
How to use this table
Scan the Size column for the millimeter stamp on your bit or the diameter on the plan. Decimal inch is a shop conversion (mm÷25.4), not a claim of lab tolerance or coating allowance. Click Find on a row to open the size finder with that label preselected — kit matching lives on the tool page, not as a product grid here. Metric labels in our Wave0 map are often default-fallback for kits (US consumer sets print fractional lids more often); the finder stays honest when a size is not explicitly mapped.
Metric steps here run common shop increments from 1mm through 12mm in the verified set. If your drawing calls 6.5mm and your case jumps from 6mm to 7mm, do not “round up” blindly for pilots in metal — check clearance versus body diameter first. For wood screws and hardware that arrived with inch guidance, cross-check the fractional split or full chart before you open the hole.
Typical flow: read the mm mark on the bit or BOM, find the row, note decimal inch if you must talk to an inch-only index, then Find → size finder for kit context. This page stays a quiet reference; the flagship chart and finder own navigation and commerce. Critical fits still need a gauge — table values are nominal workshop equivalents.
If a metric size is missing from a cheap mixed set, it can still appear here for identification. Hub chips promote mapped fractional staples only so we never advertise a kit that does not honestly include the size. Unmapped metric rows still look up; the kit card may show the default set with a default note instead of a fake “includes this size” claim.
| Size | Inch (dec) | mm | Look up |
|---|---|---|---|
| 1mm | 0.0394 | 1.00 | Find → |
| 1.5mm | 0.0591 | 1.50 | Find → |
| 2mm | 0.0787 | 2.00 | Find → |
| 2.5mm | 0.0984 | 2.50 | Find → |
| 3mm | 0.1181 | 3.00 | Find → |
| 3.5mm | 0.1378 | 3.50 | Find → |
| 4mm | 0.1575 | 4.00 | Find → |
| 4.5mm | 0.1772 | 4.50 | Find → |
| 5mm | 0.1969 | 5.00 | Find → |
| 5.5mm | 0.2165 | 5.50 | Find → |
| 6mm | 0.2362 | 6.00 | Find → |
| 6.5mm | 0.2559 | 6.50 | Find → |
| 7mm | 0.2756 | 7.00 | Find → |
| 8mm | 0.3150 | 8.00 | Find → |
| 9mm | 0.3543 | 9.00 | Find → |
| 10mm | 0.3937 | 10.00 | Find → |
| 12mm | 0.4724 | 12.00 | Find → |
FAQ
What are metric drill bit sizes?
Metric sizes are labeled in millimeters (for example 3mm, 6mm, 10mm). The decimal-inch column is a shop conversion so you can compare a metric bit to an inch plan or a fractional index case.
Is 6mm the same as 1/4"?
No. 6mm is 0.2362" nominal; 1/4" is 0.2500" (6.35mm). Close for rough work, not interchangeable for precision pilots or reamed fits. Use both columns before you force a match.
Which metric sizes are common in home kits?
Many mixed sets include 3mm, 4mm, 5mm, 6mm, 8mm, and 10mm. This table lists the verified metric rows in our dataset; click Find on a row to open the size finder with that label.
Where is the full four-system chart?
Open the drill bit size chart for fractional, metric, number, and letter together. This split page is the metric series only for faster scanning.
Sources
Metric diameters follow common published mm drill indexes used in workshop references. Decimal-inch values are nominal conversions for comparison. Confirm critical fits on the bit or with a gauge. See the site disclaimer for limits of use.