What are degrees of freedom in a robot?

How it works

A robot's configuration is a specification of where every point on it is. Northwestern University's Modern Robotics video lectures accompany the textbook by Kevin Lynch and Frank Park. They define the number of degrees of freedom as the minimum count of real numbers needed to represent that configuration. A rigid body in three-dimensional space has six: three for position and three angles, sometimes called roll, pitch and yaw.

Joints remove freedoms. The next lecture explains that a revolute joint, which rotates, or a prismatic joint, which slides, leaves one degree of freedom between the two bodies it connects. A universal joint leaves two and a ball-and-socket joint three. A robot's total equals the freedoms of its rigid bodies minus the constraints on their motion. Limits on range of motion do not reduce the count.

Industrial robot definitions use the related term axes. The International Federation of Robotics bases its definition of an industrial robot on the ISO 8373:2021 standard. It defines one as a manipulator programmable in three or more axes. It calls an axis a direction of linear or rotary motion.

Why it matters for humanoid robots

Published totals vary widely. NASA lists 44 degrees of freedom for Valkyrie, a humanoid built for the 2013 DARPA Robotics Challenge Trials. It lists seven per arm for Robonaut 2. Unitree's G1 specifications give 23 for the base model and up to 43 for the G1 EDU version with optional hands and extra waist and wrist joints. Boston Dynamics' Atlas product page, viewed in October 2026, lists 56.

Where things stand in 2026

Totals depend on what is counted. Nvidia said in June 2026 that its reference humanoid design for researchers pairs a Unitree robot with Sharpa five-finger hands. It listed 31 degrees of freedom across the body and 75 with the hands included.

Some designers hold the count down on purpose. Boston Dynamics said on October 1, 2026 that its redesigned Atlas hand has four fingers, counting the thumb, and 13 degrees of freedom, up from 7. IEEE Spectrum reported the same day that keeping the count below that of more humanlike hands allows fewer, bigger, stronger actuators. Actuators are the motors that move each joint. Alberto Rodriguez, the company's director of robot behavior, told the magazine that hand design is a "ruthless" trade-off. He said many current designs give up reliability and manufacturability.