Dice Calipers

Dice Calipers

Are your dice fair? Don't trust, verify.

Alex Waltz (a bitcoiner well known for his research and experience with entropy) was in need of a tool to check that a die is evenly weighted.

The Design - Version 1


A simple part was designed which holds a fixed brass plated steel binder (left hand side) and an M6 flanged nut (right hand side). A winged screw is rotated to gently clamp the corners of the die being tested.

Within 45 minutes of reading the tweet the part was beng manufactured - 3D printing is a remarkable technology.

Ideally concave contact faces would be used to ensure a point contact with the die. With limited hardware to hand I replicated this as best I could by clamping a steel dowel pin against the plated steel binder to create a concave surface.

Quick testing with an apropriately sized (very eccentric) brass part worked well.

All that's left is to get a casino grade dice and test it out! This page will be updated soon!

Note: An alternate way to test dice fairness without such a tool is by using salt water (to ensure the die floats). This is arguably more reliable than the clamp type design which requires sharp / well defined corner geometry for point contacts in the concave cups.

How to Salt Water test your Dice
Dice aren’t really “good” or “bad.” Rather, they’re balanced or unbalanced. This means that they can have internal flaws that are messing you up. How can you tell?A saltwater balancing test.

Version 2

Also 2022/04/02

Following discussion with @raw_avocado the dented flat brass plated binder has been switched to grub screws with conical faces for better geometric restraint.

An internal rib structure has also been added to maximise the strength to weight ratio when printing at less than 100% infill.


The conical clamping faces of the grub screws provide a superior restraint - the friction is greatly reduced meaning the part is free to rotate under the slightest eccentric load (due to an off axis centre of mass).