Differential Drive Calculator

Most mobile robots steer by driving two wheels at different speeds. The maths is short, but the details (units, signs, wheel separation, encoder counts) cause a large share of real-world bugs. The Differential Drive Calculator puts the maths in front of you with a drawing of the result.

Three calculators in one

• cmd_vel to wheels: turn a ROS Twist command into wheel speeds in m/s, rad/s, RPM and encoder ticks per second, with the turning radius and a speed limit that keeps the robot on the same curve.
• Wheels to cmd_vel: turn measured wheel speeds back into the robot's linear and angular velocity.
• Encoder odometry: turn tick counts into a new pose using the exact arc update, and compare it with the simple straight-line update.

Who it is for

Anyone writing a motor driver node, configuring diff_drive_controller, or debugging odometry that drifts. The defaults are typical of small TurtleBot-style robots.

How it is checked

The calculator uses the same unicycle model as the ROS 2 diff_drive_controller. We test it with cases that have exact answers: equal wheel travel gives a straight line, opposite wheel travel gives a turn on the spot, and an arc of known radius ends exactly where geometry says it should.

Open the Differential Drive Calculator. The guides below derive the kinematics, follow a Twist message down to the motors, build odometry from encoders, calibrate the robot and limit its motion smoothly.