3/16-Inch Drill Bit: Exact Conversion and Closest Substitutes
A 3/16-inch drill bit is exactly 4.7625 mm. Compare 4.75 mm, 4.8 mm and No. 12 substitutes—and know when to keep the specified size.
A 3/16-inch drill bit has a nominal diameter of 0.1875 inch, or exactly 4.7625 mm. A 4.75 mm bit is a close metric substitute, slightly smaller; 4.8 mm is slightly larger. The closest numbered drill is No. 12, at 0.1890 inch—not an exact match. The fractional and numbered diameters appear in this drill-size reference chart.
If the job specifically requires a 3/16-inch hole, use a 3/16-inch bit unless the permitted hole-size range allows a substitute.
Equivalent and nearby sizes
The exact conversion is 3 ÷ 16 × 25.4 = 4.7625 mm. A chart rounded to two decimal places may therefore show 4.76 mm; that does not make a 4.8 mm bit identical.
| Bit size | Nominal diameter in mm | Difference from 3/16 inch |
|---|---|---|
| No. 13 — 0.1850 in | 4.6990 | 0.0635 mm smaller |
| 4.75 mm | 4.7500 | 0.0125 mm smaller |
| 3/16 in — 0.1875 in | 4.7625 | Exact reference |
| 4.8 mm | 4.8000 | 0.0375 mm larger |
| No. 12 — 0.1890 in | 4.8006 | 0.0381 mm larger |
| 5 mm | 5.0000 | 0.2375 mm larger |
Numbered diameters are from the reference chart; metric conversions and differences are calculated from the nominal sizes.
Which substitute should you use?
- If a slightly smaller diameter is acceptable: 4.75 mm is closer than 4.8 mm. It is an actual manufactured size—for example, Guhring lists a 4.75 mm jobber drill—though your set may not include it.
- If your metric set uses 0.1 mm increments: 4.8 mm is the nearest size. Use it only if the additional diameter is acceptable for the fit.
- If you have numbered drills: No. 12 is the nearest, on the larger side. No. 13 is farther away and smaller.
- If you only have a 5 mm bit: do not treat it as equivalent. It is about 5% larger in diameter; check the required fit before using it.
For a noncritical hole, compare the proposed diameter with the clearance you need. For a fitted pin, dowel, tap-drilled hole or anchor installation, follow the drawing or product instructions rather than choosing solely by proximity.
Anchor size is not drill-bit size
A 3/16-inch fastener does not automatically require a 3/16-inch bit. For example, Tapcon’s Blue, White and Stainless performance sheet specifies a 5/32-inch bit for its 3/16-inch anchors, and a 3/16-inch bit for its 1/4-inch anchors.
When instructions call for a 3/16-inch masonry bit, keep that specified size rather than assuming a nearby metric twist bit is interchangeable. Diameter and bit type are separate checks; use the material-based drill-bit buying guide to choose the appropriate cutting design.