What is wheel odometry?

Wheel odometry estimates a robot's position and orientation by integrating wheel encoder measurements over time. Each encoder reports how many ticks (increments) the wheel has rotated; dividing ticks by the encoder's ticks-per-revolution and multiplying by wheel circumference gives distance traveled.

What is the differential drive odometry equation?

For a two-wheeled differential drive robot: distance_left = (ticks_left / TPR) × π × diameter; distance_right = (ticks_right / TPR) × π × diameter. Center distance d = (d_right + d_left) / 2; heading change Δθ = (d_right − d_left) / wheelbase. New position: x += d × cos(θ + Δθ/2); y += d × sin(θ + Δθ/2).

What are ticks per revolution (TPR)?

TPR (also called counts per revolution or CPR) is the number of encoder pulses generated per full wheel rotation. Quadrature encoders typically report 4× the line count — a 500 PPR encoder outputs 2000 TPR in quadrature mode. Check your encoder datasheet for the correct value.

Why does odometry drift over time?

Odometry integrates small errors in every step. Wheel slip, uneven surfaces, encoder quantization, and slight diameter differences between wheels all accumulate. For long runs, fuse odometry with an IMU or external sensor (LIDAR, GPS) to correct drift.

What is the wheelbase?

The wheelbase (also called track width or baseline) is the distance between the two drive wheel contact patches measured center-to-center. Accurate wheelbase measurement is critical — even a 1 mm error creates systematic heading drift.

Does this calculator handle cumulative position tracking?

Yes. Enter the robot's current X, Y, and heading as the starting pose. The tool computes the new pose after applying the encoder ticks. You can chain multiple updates by copying the output pose back as the starting pose.

Wheel Odometry Calculator

Name: Wheel Odometry Calculator
Availability: InStock
Author: Nham Vu

Enter wheel encoder ticks, wheel diameter, track width, and encoder resolution to compute robot displacement and heading change.

Robot Configuration

Wheel Diameter

Wheelbase

Ticks per Revolution (TPR)

Encoder pulses per full wheel rotation (quadrature × 4 × PPR)

Encoder Ticks (current update)

Left Wheel Ticks

Right Wheel Ticks

Starting Pose (optional)

Heading

Displacement This Update

Left Distance

—

meters

Right Distance

—

meters

Center Travel

—

meters

Heading Change (Δθ)

—

degrees

Turn Radius

—

meters

New Robot Pose

X Position

—

meters

Y Position

—

meters

Heading (θ)

—

degrees

Motion Preview

Start pose (blue arrow) → new pose (green arrow). Arc shown in orange.

Summary

Enter wheel encoder ticks, wheel diameter, track width, and encoder resolution to compute robot displacement and heading change.

How it works

Enter the left and right wheel encoder tick counts since the last update.
Input the wheel diameter and encoder ticks per revolution (TPR).
Enter the wheelbase (distance between the two wheel contact points).
Optionally set the robot's starting X, Y position and heading angle.
The calculator applies differential drive odometry equations to output displacement, heading change, and new absolute position.

Use cases

Estimate a mobile robot's position during autonomous navigation without GPS.
Debug wheel encoder readings and verify they match expected travel distance.
Prototype dead-reckoning navigation before implementing sensor fusion with IMU or LIDAR.
Calculate the arc length and turning radius during curved motion segments.
Validate robot kinematics after changing wheel diameter, encoder, or gearbox.
Teach differential drive odometry math in robotics coursework or workshops.

Frequently Asked Questions

Last updated: 2026-07-26 · Reviewed by Nham Vu