--- title: "Humanoid robot actuators: joint-by-joint guide" description: "Humanoid robot actuators by joint: static torque estimates for hip, knee, ankle, shoulder, elbow and wrist, with catalog shortlists and open unknowns." canonical: https://actuatorlist.com/guides/humanoid-robot-actuators last-updated: 2026-10-04 --- # Humanoid robot actuators: what each joint needs and which catalog parts reach it A humanoid has no single right actuator: each joint loads its motor differently. Pick a numbered joint for its static torque estimate and the catalog parts that reach it. ## How to read this guide The reference robot is **hypothetical**: 1.5 m tall, 50 kg, carrying 1 kg in one hand. Every torque below is a **static engineering estimate** (mass × g × horizontal lever arm) for one stated pose, rounded to one decimal place. Static torque is a floor. Walking, stairs, recovery steps and impacts add dynamic torque that depends on your gait and controller, and this guide does not estimate it. Each shortlist screens catalog entries tagged for humanoid joints. An entry passes when its documented rated torque covers the estimate (listed first) or, failing that, its documented peak torque does (short duty only). Undocumented torque never passes. Use the [robot arm torque calculator](/tools/robot-arm-torque-calculator) to size your own arm joint by joint, the [motor torque calculator](/tools/motor-torque-calculator) to screen the whole catalog at your own torque and speed, and the [actuator selection guide](/guides/robot-actuator-selection) for the efficiency, thermal, precision and sim2real checks a shortlist does not settle. ## Shoulder Shoulder pitch carries the whole arm and its payload when the arm reaches forward. It is the highest-torque arm joint, and its actuator mass sits close to the torso, where it costs little extra torque elsewhere. **Estimate: 12.7 N·m static.** Typical DOF: 2–3 (pitch, roll, yaw). Pose: arm straight out in front: a 3 kg arm with its center of mass 0.25 m out, plus the 1 kg payload at 0.55 m. Working: 3 × 9.807 × 0.25 + 1 × 9.807 × 0.55 = 12.7 N·m. **Catalog screen** (22 humanoid-tagged entries pass; lightest rated fits first): - [ENCOS EC-A3814-H14-107](/actuators/encos-ec-a3814-h14-107): rated 20 N·m, peak 60 N·m, mass 434 g. Rated torque covers it. - [ENCOS EC-A4315-P2-36](/actuators/encos-ec-a4315-p2-36): rated 25 N·m, peak 75 N·m, mass 485 g. Rated torque covers it. - [ENCOS EC-A5013-H17-100](/actuators/encos-ec-a5013-h17-100): rated 30 N·m, peak 90 N·m, mass 630 g. Rated torque covers it. - [DAMIAO (DMBots) DM-J6248P-2EC](/actuators/damiao-dm-j6248p-2ec): rated 30 N·m, peak 97 N·m, mass 660 g. Rated torque covers it. [Compare these 4](/compare?compare=damiao-dm-j6248p-2ec,encos-ec-a3814-h14-107,encos-ec-a4315-p2-36,encos-ec-a5013-h17-100). ## Elbow The elbow carries only the forearm, hand and payload, but its actuator mass hangs on the upper arm and adds to the shoulder's load. Mass per unit of torque matters more here than at the shoulder. **Estimate: 4.4 N·m static.** Typical DOF: 1 (pitch). Pose: forearm horizontal: 1.2 kg forearm and hand at 0.12 m, plus the payload at 0.30 m. Working: 1.2 × 9.807 × 0.12 + 1 × 9.807 × 0.3 = 4.4 N·m. **Catalog screen** (24 humanoid-tagged entries pass; lightest rated fits first): - [RobStride 00](/actuators/robstride-00): rated 5 N·m, peak 14 N·m, mass 310 g. Rated torque covers it. - [DAMIAO (DMBots) DM-J4340-2EC](/actuators/damiao-dm-j4340-2ec): rated 9 N·m, peak 27 N·m, mass 362 g. Rated torque covers it. - [RobStride 01](/actuators/robstride-01): rated 6 N·m, peak 17 N·m, mass 380 g. Rated torque covers it. - [RobStride 02](/actuators/robstride-02): rated 6 N·m, peak 17 N·m, mass 380 g. Rated torque covers it. [Compare these 4](/compare?compare=damiao-dm-j4340-2ec,robstride-00,robstride-01,robstride-02). ## Wrist Wrist torque is small. Size, mass and backlash at the end of a long lever set the choice. Every gram here is multiplied by the full arm length at the shoulder. **Estimate: 1.0 N·m static.** Typical DOF: 1–3 (pitch, yaw, roll). Pose: hand horizontal: the payload at 0.08 m and a 0.4 kg hand at 0.05 m. Working: 1 × 9.807 × 0.08 + 0.4 × 9.807 × 0.05 = 1.0 N·m. **Catalog screen** (24 humanoid-tagged entries pass; lightest rated fits first): - [DAMIAO (DMBots) DM-J4310-2EC](/actuators/damiao-dm-j4310-2ec): rated 3 N·m, peak 7 N·m, mass 306 g. Rated torque covers it. - [RobStride 00](/actuators/robstride-00): rated 5 N·m, peak 14 N·m, mass 310 g. Rated torque covers it. - [DAMIAO (DMBots) DM-J4340-2EC](/actuators/damiao-dm-j4340-2ec): rated 9 N·m, peak 27 N·m, mass 362 g. Rated torque covers it. - [RobStride 01](/actuators/robstride-01): rated 6 N·m, peak 17 N·m, mass 380 g. Rated torque covers it. [Compare these 4](/compare?compare=damiao-dm-j4310-2ec,damiao-dm-j4340-2ec,robstride-00,robstride-01). ## Waist Waist pitch holds the upper body when it leans. Waist yaw sees little gravity load; its torque comes from accelerating the upper body's inertia, which depends on your motion and is not estimated here. **Estimate: 16.9 N·m static.** Typical DOF: 1–3 (yaw, pitch, roll). Pose: a 20 kg upper body with its center of mass 0.25 m above the waist, leaning 20°, so 0.086 m forward. Working: 20 × 9.807 × 0.086 = 16.9 N·m. **Catalog screen** (21 humanoid-tagged entries pass; lightest rated fits first): - [ENCOS EC-A3814-H14-107](/actuators/encos-ec-a3814-h14-107): rated 20 N·m, peak 60 N·m, mass 434 g. Rated torque covers it. - [ENCOS EC-A4315-P2-36](/actuators/encos-ec-a4315-p2-36): rated 25 N·m, peak 75 N·m, mass 485 g. Rated torque covers it. - [ENCOS EC-A5013-H17-100](/actuators/encos-ec-a5013-h17-100): rated 30 N·m, peak 90 N·m, mass 630 g. Rated torque covers it. - [DAMIAO (DMBots) DM-J6248P-2EC](/actuators/damiao-dm-j6248p-2ec): rated 30 N·m, peak 97 N·m, mass 660 g. Rated torque covers it. [Compare these 4](/compare?compare=damiao-dm-j6248p-2ec,encos-ec-a3814-h14-107,encos-ec-a4315-p2-36,encos-ec-a5013-h17-100). ## Hip In single-leg stance the hip must hold the rest of the body against tipping sideways (hip roll) and forward (hip pitch). Hip actuators sit at the pelvis, so their mass is cheap to carry, and they are usually among the largest in the robot. **Estimate: 41.2 N·m static.** Typical DOF: 3 (pitch, roll, yaw). Pose: single-leg stance: the 42 kg above the stance hip, with its center of mass 0.10 m to the side. Working: 42 × 9.807 × 0.1 = 41.2 N·m. **Catalog screen** (15 humanoid-tagged entries pass; lightest rated fits first): - [Robotis (Dynamixel) PH54-200-S500-R (Dynamixel-P / Pro+)](/actuators/dynamixel-ph54-200-s500-r): rated 44.7 N·m, peak 73 N·m, mass 855 g. Rated torque covers it. - [MyActuator RMD-X8-120](/actuators/myactuator-rmd-x8-120): rated 43 N·m, peak 120 N·m, mass 1400 g. Rated torque covers it. - [MyActuator RMD-X10-S2 V3 (1:35)](/actuators/myactuator-rmd-x10-s2-v3): rated 50 N·m, peak 100 N·m, mass n/a. Rated torque covers it. - [ENCOS EC-A3814-H14-107](/actuators/encos-ec-a3814-h14-107): rated 20 N·m, peak 60 N·m, mass 434 g. Peak only: short duty. [Compare these 4](/compare?compare=dynamixel-ph54-200-s500-r,encos-ec-a3814-h14-107,myactuator-rmd-x10-s2-v3,myactuator-rmd-x8-120). ## Knee The knee usually needs the most torque in the leg: rising from a crouch or landing a step puts body weight on a bent knee with a long lever. A knee that must also absorb impacts benefits from backdrivability, which the catalog records when documented. **Estimate: 69.1 N·m static.** Typical DOF: 1 (pitch). Pose: single-leg stance on a bent knee: 47 kg above the knee, center of mass 0.15 m behind it. Working: 47 × 9.807 × 0.15 = 69.1 N·m. **Catalog screen** (11 humanoid-tagged entries pass; lightest first): - [ENCOS EC-A4315-P2-36](/actuators/encos-ec-a4315-p2-36): rated 25 N·m, peak 75 N·m, mass 485 g. Peak only: short duty. - [ENCOS EC-A5013-H17-100](/actuators/encos-ec-a5013-h17-100): rated 30 N·m, peak 90 N·m, mass 630 g. Peak only: short duty. - [DAMIAO (DMBots) DM-J6248P-2EC](/actuators/damiao-dm-j6248p-2ec): rated 30 N·m, peak 97 N·m, mass 660 g. Peak only: short duty. - [ENCOS EC-A6416-P2-25](/actuators/encos-ec-a6416-p2-25): rated 40 N·m, peak 120 N·m, mass 805 g. Peak only: short duty. No humanoid-tagged entry documents a rated torque this high. Holding this load continuously needs a larger actuator, more reduction, a linkage with mechanical advantage, or a duty cycle confirmed against the peak rating. [Compare these 4](/compare?compare=damiao-dm-j6248p-2ec,encos-ec-a4315-p2-36,encos-ec-a5013-h17-100,encos-ec-a6416-p2-25). ## Ankle The ankle balances the body over the foot, so its torque grows with how far the center of pressure moves from the ankle axis. Its actuator is the most distal mass in the leg, which is why many designs place the ankle motors higher on the shank and drive the ankle through linkages; with a linkage, the motor-side torque differs from the joint torque by the linkage ratio. **Estimate: 38.4 N·m static.** Typical DOF: 2 (pitch, roll). Pose: single-leg stance with the center of pressure 0.08 m from the ankle axis: 49 kg above the ankle. Working: 49 × 9.807 × 0.08 = 38.4 N·m. **Catalog screen** (15 humanoid-tagged entries pass; lightest rated fits first): - [ENCOS EC-A6416-P2-25](/actuators/encos-ec-a6416-p2-25): rated 40 N·m, peak 120 N·m, mass 805 g. Rated torque covers it. - [Robotis (Dynamixel) PH54-200-S500-R (Dynamixel-P / Pro+)](/actuators/dynamixel-ph54-200-s500-r): rated 44.7 N·m, peak 73 N·m, mass 855 g. Rated torque covers it. - [MyActuator RMD-X8-120](/actuators/myactuator-rmd-x8-120): rated 43 N·m, peak 120 N·m, mass 1400 g. Rated torque covers it. - [RobStride 04](/actuators/robstride-04): rated 40 N·m, peak 120 N·m, mass 1420 g. Rated torque covers it. [Compare these 4](/compare?compare=dynamixel-ph54-200-s500-r,encos-ec-a6416-p2-25,myactuator-rmd-x8-120,robstride-04). ## What this guide does not establish - **Which actuators commercial humanoids use.** Product photos, teardowns and press coverage rarely confirm the exact installed model and revision. This guide treats installed components as unknown unless a manufacturer documents them. - **Dynamic and thermal duty.** A joint that holds its static estimate for minutes needs rated (continuous) torque at the installed cooling; peak torque is time-limited. Duty depends on the gait, the controller and the enclosure. - **A best joint actuator.** Each joint trades torque density against something else. Mass at the wrist, backdrivability at the knee and envelope at the ankle pull in different directions. - **Torque–speed envelopes.** A catalog rating is one point. Confirm torque at the joint speeds your gait needs, at your bus voltage. - **Torque for every tagged entry.** These humanoid-tagged entries document no torque, so they never pass a screen: [ODrive S1](/actuators/odrive-s1), [ODrive Pro](/actuators/odrive-pro), [mjbots moteus r4.11](/actuators/mjbots-moteus-r4-11), [Nidec Drive Technology (Nidec-Shimpo) Smart-FLEXWAVE SRH series (smart strain-wave reducer)](/actuators/nidec-smart-flexwave-srh). Most are drives or reducers that need a motor or driver to form a joint. ## Next steps Pick two to four candidates per joint and open them in [Compare](/compare). Check each candidate's sources and revision on its catalog page. Then work through the [selection guide](/guides/robot-actuator-selection): mission energy, warm duty, loaded repeatability and a held-out model fit, measured on the installed joint.