Degrees of freedom (DoF)

What it means

In mechanics, the degrees of freedom of a system are the number of independent parameters needed to fully specify its configuration or state. A rigid body in three-dimensional space has at most six: three of translation and three of rotation. A joint provides one degree of freedom if it is a hinge or sliding joint, and two if it is cylindrical.

For a robot, the count is usually the number of independent motions its joints allow. Wikipedia's example is a serial manipulator built from six joints, each providing one degree of freedom, which therefore has six in total.

How it applies to humanoid robots

A humanoid's total is the sum of its controllable joint motions across the body: legs, waist, arms and, in some designs, hands, wrists, neck and head. Wikipedia's humanoid robot article notes that more degrees of freedom give a robot more redundancy of movement and therefore a wider range of tasks. A high total is a design feature, not proof that a robot performs any particular task well.

Unitree's G1 shows how a total is built up. The base version is listed at 23 degrees of freedom: six per leg, five per arm and one at the waist. The EDU version adds optional waist, hand and wrist joints, and Unitree lists its total as 23 to 43 depending on options.

Counting and terminology caveats

Totals are only comparable when the same parts are counted. Hands, wrists and waists are common sources of difference, as the G1 case shows: the base total leaves out hands, while the EDU range includes optional hand and wrist joints. Always check the note for what a total includes.

Action-space dimensions are not joint counts. Figure says its Helix model coordinates a 35-DoF action space at 200 Hz and controls the upper body. That number describes what the controller outputs, which may not map one-to-one onto the robot's mechanical joints.

More degrees of freedom are not automatically better. A 2025 arXiv paper comparing human and robotic hands asks whether robots need anthropomorphic hands at all; its abstract favours robustness and softness over copying the number of fingers and degrees of freedom.

How to read the numbers on humanoidversus.com

The dof_total field is the total that the maker or a cited source gives for the base or most common version. The note says whether hands are included and what an EDU or other variant adds. A null means no sourced total was found; it does not mean zero.

The live ranking sorts robots by dof_total, and dof_per_hand is shown separately because hands are counted in different ways. Compare totals only after checking the note for what they include, such as whether wrists or end effectors are counted.

Further reading

For background, see the Wikipedia article on degrees of freedom in mechanics, the humanoid robot article, Unitree's G1 product page, Figure's Helix announcement and the 2025 arXiv paper by Fabisch et al. on anthropomorphic hands.