Looks up standard square/parallel key width and height for a given shaft diameter (ANSI inch square keys or DIN 6885 metric parallel keys), and gives the nominal keyseat depth in the shaft and keyway depth in the hub.
Inputs
Results
Depths shown are the common nominal half-height split (h÷2 each side), which covers most general-purpose designs. For tight-tolerance or high-load applications, verify exact t1 (shaft) / t2 (hub) values against the full ANSI B17.1 or DIN 6885-1 standard, since published tables sometimes split the height unevenly.
Reference Tables
| Shaft Dia. Range (in) | Key W × H (in) |
|---|---|
| 0.3125–0.4375 | 0.094 × 0.094 |
| 0.4375–0.5625 | 0.125 × 0.125 |
| 0.5625–0.875 | 0.188 × 0.188 |
| 0.875–1.25 | 0.25 × 0.25 |
| 1.25–1.375 | 0.3125 × 0.3125 |
| 1.375–1.75 | 0.375 × 0.375 |
| 1.75–2.25 | 0.5 × 0.5 |
| 2.25–2.75 | 0.625 × 0.625 |
| 2.75–3.25 | 0.75 × 0.75 |
| 3.25–3.75 | 0.875 × 0.875 |
| 3.75–4.5 | 1.0 × 1.0 |
| Shaft Dia. Range (mm) | Key b × h (mm) |
|---|---|
| 6–8 | 2 × 2 |
| 8–10 | 3 × 3 |
| 10–12 | 4 × 4 |
| 12–17 | 5 × 5 |
| 17–22 | 6 × 6 |
| 22–30 | 8 × 7 |
| 30–38 | 10 × 8 |
| 38–44 | 12 × 8 |
| 44–50 | 14 × 9 |
| 50–58 | 16 × 10 |
| 58–65 | 18 × 11 |
| 65–75 | 20 × 12 |
| 75–85 | 22 × 14 |
| 85–95 | 25 × 14 |
| 95–110 | 28 × 16 |
How It Works
Standard key sizes are not calculated from a formula — they are looked up from a published table based on shaft diameter, since key cross-sections are standardized in discrete steps for tooling and stocking reasons. This calculator matches your shaft diameter to the correct range and reports the standard width and height, along with the nominal keyseat/keyway depth split.
FAQ
Why is my shaft diameter on the edge of two ranges? Use the larger key size if you are unsure, since an oversized key is generally safer for torque transmission than an undersized one — but always confirm against your actual standard reference and any existing mating parts.
Square key vs. parallel (rectangular) key — does it matter here? ANSI square keys have b = h by definition for smaller shafts; DIN 6885 parallel keys are rectangular (b ≠ h) for larger sizes. The lookup table already reflects this, so just pick the correct standard for your drawing.
Related Guides
ISO Hole/Shaft Fit & Tolerance Calculator · Hole Pattern Calculator