REFERENCE / WIDTHS
Eurorack HP to mm: the full conversion table
1 HP = 5.08 mm on the rails. A front panel is cut a few tenths narrower than its pitch so modules can be screwed side by side, which is why a 6 HP panel is 30.00 mm wide and not 30.48 mm.
HP to mm, 1 to 42 HP
| WIDTH | RAIL PITCH (MM) | PANEL WIDTH (MM) | SOURCE |
|---|---|---|---|
| 1 HP | 5.08 | 5.00 | DOEPFER |
| 1.5 HP | 7.62 | 7.50 | DOEPFER |
| 2 HP | 10.16 | 9.80 | DOEPFER |
| 3 HP | 15.24 | 14.89 | DERIVED |
| 4 HP | 20.32 | 20.00 | DOEPFER |
| 5 HP | 25.40 | 25.05 | DERIVED |
| 6 HP | 30.48 | 30.00 | DOEPFER |
| 7 HP | 35.56 | 35.21 | DERIVED |
| 8 HP | 40.64 | 40.30 | DOEPFER |
| 9 HP | 45.72 | 45.37 | DERIVED |
| 10 HP | 50.80 | 50.50 | DOEPFER |
| 11 HP | 55.88 | 55.53 | DERIVED |
| 12 HP | 60.96 | 60.60 | DOEPFER |
| 13 HP | 66.04 | 65.69 | DERIVED |
| 14 HP | 71.12 | 70.80 | DOEPFER |
| 15 HP | 76.20 | 75.85 | DERIVED |
| 16 HP | 81.28 | 80.90 | DOEPFER |
| 17 HP | 86.36 | 86.01 | DERIVED |
| 18 HP | 91.44 | 91.30 | DOEPFER |
| 19 HP | 96.52 | 96.17 | DERIVED |
| 20 HP | 101.60 | 101.30 | DOEPFER |
| 21 HP | 106.68 | 106.30 | DOEPFER |
| 22 HP | 111.76 | 111.40 | DOEPFER |
| 23 HP | 116.84 | 116.49 | DERIVED |
| 24 HP | 121.92 | 121.57 | DERIVED |
| 25 HP | 127.00 | 126.65 | DERIVED |
| 26 HP | 132.08 | 131.73 | DERIVED |
| 27 HP | 137.16 | 136.81 | DERIVED |
| 28 HP | 142.24 | 141.90 | DOEPFER |
| 29 HP | 147.32 | 146.97 | DERIVED |
| 30 HP | 152.40 | 152.05 | DERIVED |
| 31 HP | 157.48 | 157.13 | DERIVED |
| 32 HP | 162.56 | 162.21 | DERIVED |
| 33 HP | 167.64 | 167.29 | DERIVED |
| 34 HP | 172.72 | 172.37 | DERIVED |
| 35 HP | 177.80 | 177.45 | DERIVED |
| 36 HP | 182.88 | 182.53 | DERIVED |
| 37 HP | 187.96 | 187.61 | DERIVED |
| 38 HP | 193.04 | 192.69 | DERIVED |
| 39 HP | 198.12 | 197.77 | DERIVED |
| 40 HP | 203.20 | 202.85 | DERIVED |
| 41 HP | 208.28 | 207.93 | DERIVED |
| 42 HP | 213.36 | 213.00 | DOEPFER |
Why a panel is narrower than its pitch
If every panel were cut at exactly HP × 5.08 mm, two modules side by side would touch and the screws would bind. Doepfer therefore publishes a width per size, and the reduction is not constant: 0.08 mm at 1 HP, 0.48 mm at 6 HP. For the widths that table leaves out, a clearance of 0.35 mm is taken off the pitch.
Millimeters back to HP
Divide by 5.08 and round up: a panel of 63 mm occupies 13 HP of rack space, because 12 HP would be 60.96 mm. Rack space is always counted in whole HP, even when the panel itself is narrower.
The HP and U calculator does it for any width, and gives the height of the row as well.
Questions
How many millimeters is 1 HP?
1 HP is 5.08 mm, one fifth of an inch. It is the pitch of the mounting holes on the rails, not the width a panel is cut at.
How wide is a 12 HP Eurorack panel?
A 12 HP panel takes 60.96 mm on the rails and is cut 60.60 mm wide, as published in the Doepfer A-100 construction details.
How do I convert millimeters back to HP?
Divide by 5.08 and round up: a 60 mm panel takes 12 HP of rack space. Rounding down would leave the module overlapping its neighbour.
Sources
Widths and the mounting grid come from the Doepfer A-100 construction details, table 1. The same numbers are applied by the editor in panelFormat.ts.
Draw it instead of measuring it
Eurorack Panel Designer applies every number on this page automatically: pick a width in HP or millimeters, drop the parts, and export an STL, an SVG, a PNG or a KiCad Edge.Cuts outline. It runs in the browser, it is free, and it needs no account.
Open the editor