Nut & washer sizes
A nut is named after the screw it fits, not the spanner it takes — an M3 nut needs a 5.5 mm spanner. Here is the whole set.
| Screw | Spanner | Nut height | Washer outside | Washer hole | Washer thick |
|---|---|---|---|---|---|
| M1.2 | 3 mm | 1 mm | 3.5 mm | 1.3 mm | 0.3 mm |
| M1.4 | 3 mm | 1.2 mm | 3.5 mm | 1.5 mm | 0.3 mm |
| M1.6 | 3.2 mm | 1.3 mm | 4 mm | 1.7 mm | 0.3 mm |
| M2 | 4 mm | 1.6 mm | 5 mm | 2.2 mm | 0.3 mm |
| M2.5 | 5 mm | 2 mm | 6 mm | 2.7 mm | 0.5 mm |
| M3 | 5.5 mm | 2.4 mm | 7 mm | 3.2 mm | 0.5 mm |
| M4 | 7 mm | 3.2 mm | 9 mm | 4.3 mm | 0.8 mm |
| M5 | 8 mm | 4 mm | 10 mm | 5.3 mm | 1 mm |
| M6 | 10 mm | 5 mm | 12 mm | 6.4 mm | 1.6 mm |
Standard hex nuts to DIN 934 / ISO 4032 and plain washers to DIN 125 / ISO 7089. Thin (jam) nuts are roughly half the height shown.
Which washer to use
- Plain washer — spreads the load, protects a soft or painted surface.
- Spring (split) washer — light vibration resistance, common but not the best answer.
- Serrated / tooth washer — bites in and holds better than a spring washer.
- Nylon insert nut (nyloc) — the most reliable way to stop a nut backing off.
- Fender / penny washer — extra-wide, for thin sheet or oversized holes.
Gear for this job
Affiliate links — they cost you nothing extra and keep this database free.
Metric nut assortment
Plain, nylon-insert and flange nuts
Washer assortment kit
Flat, spring and fender washers in one box