M1.6 vs M2.5
They differ by 0.9 mm across the threads — enough that they are never interchangeable, but little enough that they are easy to mix up in a parts tray.
| M1.6 | M2.5 | |
|---|---|---|
| Thread diameter | 1.60 mm | 2.50 mm |
| Standard pitch | 0.35 mm | 0.45 mm |
| Tap drill | 1.25 mm | 2.05 mm |
| Clearance hole | 1.8 mm | 2.9 mm |
| Cap head Ø | 3 mm | 4.5 mm |
| Hex key | 1.5 mm | 2.0 mm |
| Torque into steel | 12-20 N·cm | 45-70 N·cm |
| Into plastic | 6-10 N·cm | 20-35 N·cm |
M1.6 is normally used for
Laptop hinges and boards, connectors, small standoffs, instrument panels
Everything M1.6 fits →M2.5 is normally used for
The classic laptop bottom-case screw, hard drive cages, Raspberry Pi mounting holes
Everything M2.5 fits →If you are not sure which one you have
Measure across the outside of the threads with a caliper. A reading within about 0.1 mm of the nominal size is your answer — 1.6 mm means M1.6, 2.5 mm means M2.5.
Use the screw size finder →Buy either size
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M1.6 screws
Assorted lengths in one box
M2.5 screws
Assorted lengths in one box
Digital caliper
Tells the two sizes apart for certain