M4 Screw Hole Size
The right hole size for an M4 screw depends on one question: should the screw pass through the part (a clearance hole) or thread into it (a tapped hole)? The short answer: 4.3–4.8 mm for clearance, 3.3 mm for a tap drill. Here are the exact numbers and when to use each.
M4 clearance hole (screw passes through)
A clearance hole lets the M4 screw’s 4 mm shank slide straight through without binding. The standard sizes:
| Fit | Hole diameter | Use when |
|---|---|---|
| Close | 4.3 mm | Precise alignment, snug fit |
| Normal | 4.5 mm | Most general use |
| Loose | 4.8 mm | Easy assembly, some play |
When in doubt, 4.5 mm is the safe default. Need the same numbers for M3, M5, and up? The full table is in the metric clearance hole size chart, and the bolt-focused version is the bolt hole size chart.
M4 tapped hole (threading into the part)
To cut M4 threads directly into a part, you drill a smaller tap drill hole first, then run an M4 tap. For standard coarse M4 (0.7 mm pitch), the tap drill is 3.3 mm.
| Hole type | M4 diameter |
|---|---|
| Tap drill (coarse, 0.7 mm pitch) | 3.3 mm |
| Clearance (normal) | 4.5 mm |
Tapping works in metal. In plastic and 3D prints, cut threads strip easily — use a heat-set insert instead, which needs a straight hole sized to the insert. See heat-set inserts for 3D printing and how to add threads to a part.
M4 holes for 3D printing
Printed holes come out smaller than designed — the plastic squeezes inward and the first layer can sag. For a 3D-printed M4 clearance hole, start one size up (around 4.8–5.0 mm modeled) and test-fit; widen if the screw binds. The reasons and a general fit guide are in tolerances for 3D printed parts.
Designing the part that holds the hole? Mind the wall around it — see wall thickness for 3D printing.
Put an M4 hole in your part
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