Robot Arm Torque Calculator
Combine payload, tooling, and arm mass to approximate the torque required at a joint, then apply acceleration and safety factors to choose motors, gearboxes, or brakes with sufficient headroom.
Breaking down the torque terms
The arm must counter both gravity and any commanded acceleration. Treat the distributed arm mass as acting at its midpoint, so the effective mass at the end of the joint is . Static torque is then , where is the segment length.
Dynamic torque depends on the desired angular acceleration . The tangential acceleration at the payload is , and the torque to deliver that acceleration is . Applying a safety factor and dividing by gearbox efficiency converts the joint torque into motor shaft torque so you can compare against catalog ratings.
Benchmark cases
| Application | Payload (kg) | Length (m) | Acceleration (deg/s²) | Total torque (N·m) |
|---|---|---|---|---|
| Pick-and-place with light tooling | 3.0 | 0.45 | 180 | 23.7 |
| Packaging robot lifting cartons | 10.0 | 0.65 | 120 | 82.5 |
| Heavy assembly workstation | 18.0 | 0.85 | 90 | 178.6 |
Continue your robot design
Pair the torque output with the Gyroscope Precession Calculator to study stability, confirm uptime planning in the Robotics Preventive Maintenance Downtime Calculator, and coordinate throughput goals using the Warehouse Robot Fleet Throughput Calculator.