CAN Bus Termination & Stub Calculator
Verify CAN/CAN-FD termination, max stub length, and bus length for specified bit rate. Prevents reflections on automotive and industrial buses.
How to Use
- Enter CAN bit rate (500 kbps classic, up to 8 Mbps CAN-FD).
- Tool gives max bus length and max stub length for that bit rate.
Show Work
CAN Spec Limits
History of CAN
Robert Bosch GmbH developed CAN (Controller Area Network) in 1983 for automotive in-vehicle networking; Mercedes-Benz first deployed it in the 1991 S-Class. CAN's differential twisted-pair with 120-ohm termination became ISO 11898-2 in 1993. CAN-FD (Flexible Data Rate, 2012) doubled then quadrupled the data rate. Modern vehicles run multiple segmented CAN buses alongside Ethernet and LIN, but CAN remains the safety-critical workhorse for powertrain, brake, and airbag signaling.
About This Calculator
Enter bit rate, node count, and cable velocity factor (0.66 for PVC-insulated twisted pair, 0.8 for foam dielectric). The tool computes max bus length and max stub length per ISO 11898-2 guidance.
Terminate the bus with 120Ω at BOTH ends (never in the middle). For EMI-sensitive designs use split termination (2×60Ω + 4.7nF to ground). Add 10-47 kΩ bias to Vdd/Vss on each terminator for reliable dominant/recessive arbitration. Everything runs client-side.
About the CAN Bus Termination & Stub Calculator
The CAN Bus Termination & Stub Calculator is a simple, free helper for electronics and circuit design that runs entirely on your own device. Verify CAN/CAN-FD termination, max stub length, and bus length for specified bit rate. Prevents reflections on automotive and industrial buses.
How it works
Enter your figures and the result appears instantly, updating the moment you change anything. There is no submit button and nothing to wait for, so it is easy to try a few what-if numbers and compare the results. Just check each box holds the kind of value it expects.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
Why 120Ω?
CAN uses twisted pair with characteristic impedance Z₀ = 120Ω. Terminators at each end match this to prevent reflections. Two 60Ω in parallel (one at each bus end) = 120Ω.
Split termination?
Two 60Ω resistors per end with a small cap to ground between them. Improves EMI performance by giving common-mode signals a path to ground. Typical 60Ω + 60Ω + 4.7nF to GND at midpoint.
Max stubs?
Stub = node-to-bus tap. Max length scales inversely with bit rate: 0.3m at 500 kbps, 0.03m (3 cm!) at 5 Mbps CAN-FD. Long stubs cause reflections and bit errors.
How do I use the CAN Bus Termination & Stub Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Does it cost anything or need an account?
No. The tool is completely free, there is no account to create, and it keeps working offline after the page first loads.
Is anything I type uploaded?
No. The tool works entirely on your device, so the values you enter never leave your browser.
Common Use Cases
Automotive 500 kbps
Max bus 40 m, max stub 0.3 m. Standard OBD-II / powertrain CAN.
Industrial 250 kbps
Max bus 250 m with shielded cable. Factory automation, CANopen.
CAN-FD 5 Mbps
Max bus 10 m, max stub 3 cm. Automotive high-speed ECU comms.
Last updated: