EURORACK SIZES: What Does “HP” Mean?
When browsing Eurorack modules, you’ll notice each one lists its size in HP. If you’re new, this can be confusing, so let’s break it down.
The Basics
All Eurorack modules are the same height: 3U (about 128.5 mm).
The width is what changes — and it’s measured in HP (Horizontal Pitch).
1 HP = 5.08 mm wide.
So when you see a module listed as “6 HP,” that means it takes up about 30.5 mm of space in your rack.
Your Eurorack case has a limited number of HP (often written as “84 HP,” “104 HP,” or “168 HP” per row).
Every module you install uses some of that width. If your case row is 84 HP wide and you install:
One 6 HP module
One 10 HP module
One 20 HP module
You’ve used up 36 HP total, leaving 48 HP for more modules.
Why HP Matters
On the front panel of each module are small holes at the edges — these line up with the rails of your case.
Screws go here to secure the module in place.
Mounting Holes
Besides the width (HP), each module has a depth measurement.
That’s how far the circuit boards and components stick out behind the panel.
Most modern cases are deep enough for most modules.
Skiff cases (the very shallow ones) sometimes need extra attention — always check the depth spec if you’re unsure.
Depth Matters, Too
Height is always 3U.
Width is in HP (1 HP = 5.08 mm).
Your case’s total HP per row limits how many modules you can fit.
Depth matters if your case is very shallow.