Calculate CAN bus load from first principles. Enter your message ID types, data lengths, and cycle rates. The tool computes total bus utilisation as a percentage of available bandwidth.

CAN Bus Load Calculator

Bus Configuration

Bus Type

Nominal Bitrate [kbps]

Arbitration phase bitrate. CAN FD uses this for header and trailer.

Data Phase Bitrate [kbps]

CAN FD only. Used after BRS bit for the data field and CRC.

Calculation Parameters

Bit-stuffing Mode

Average uses a 1.15× multiplier on the stuffable region (industry convention). Worst-case adds the maximum theoretically possible stuff bits per ISO 11898-1. Off disables stuffing entirely — raw frame bits only.

Error Frame Reserve [%]

Headroom added on top of the calculated load to account for error/overload frames. Typical 1–3% on noisy buses; leave at 0 for nominal.

BRS (CAN FD)

CAN FD only. When disabled the data phase stays at the nominal bitrate.

Message Groups

ID Type	# Messages	Data [bytes]	Cycle [ms]	Bits / Frame	Group Load

Data [bytes] — Classical CAN accepts 0–8. CAN FD accepts 0–8 byte-wise plus 12, 16, 20, 24, 32, 48, 64. Other values are rounded up to the next valid size.
Bits / Frame — total bits transmitted per frame (including stuffing, headers, CRC, IFS).

Bus Load Result

Total Bus Load: —

Effective Bitrate Used: —

Total Frames / Second: —

Stuffing Mode: —

Sources — Frame size formulas derive from ISO 11898-1. Classical CAN: base = 47 + 8·DLC (standard) or 67 + 8·DLC (extended) bits, plus stuffing on SOF…CRC. CAN FD: arbitration phase at nominal rate, data phase at data rate (when BRS enabled), CRC-17 for ≤8 B and CRC-21 for >8 B, plus 4–5 fixed stuff bits in the CRC.

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