What Are HDMI Type A Dimensions and Pin Count?

The standard HDMI Type A plug is the ubiquitous interface used to transmit high-definition digital video and multi-channel audio between consumer electronics. Defined by the HDMI specification, this standard connector features an asymmetric, 19-pin design within a compact metal housing measuring approximately 13.9 mm in width, 4.45 mm in height, and roughly 9.5 mm to 10.5 mm in mating depth. Understanding these exact mechanical specifications and pin configurations is essential for hardware design, cable manufacturing, and device integration.

Standard HDMI Type A Physical Dimensions

The HDMI Type A plug utilizes a trapezoidal, keyed form factor to prevent improper orientation during insertion. The official mechanical specifications define precise outer shell tolerances to guarantee interoperability across consumer hardware:

• Outer Width: 13.9 mm (nominal outer shell dimension at the widest edge)
• Outer Height: 4.45 mm (nominal outer shell thickness)
• Mating Length: Approximately 9.5 mm to 10.5 mm (the length of the plug section inserted into the receptacle)
• Contact Pitch: 0.5 mm centerline-to-centerline pin spacing arranged along two internal horizontal contact planes
• Shell Bevel: The bottom corners are angled inward at standard 45-degree chamfers, providing the signature asymmetric keying

The corresponding Type A receptacle has an internal opening designed to match these dimensions with strict sub-millimeter tolerances, ensuring snug mechanical engagement and consistent electrical contact with grounding fingers.

Total Pin Count and Internal Structure

A standard HDMI Type A connector features exactly 19 pins. These internal pins are divided unevenly across two rows: the upper row contains 10 pins (designated by odd numbers 1 through 19), and the lower row contains 9 pins (designated by even numbers 2 through 18).

The 19 pins are partitioned into several dedicated signal groups to maintain high-speed transmission integrity and provide auxiliary communication:

• TMDS Data Channels (Pins 1–9): Transition-Minimized Differential Signaling channels 0, 1, and 2 carry digital audio and video payloads. Each channel utilizes three dedicated pins: positive differential (+), negative differential (-), and an individual shield/ground pin to minimize cross-talk.
• TMDS Clock Channel (Pins 10–12): Carries the differential clock signal (clock +, clock shield, and clock -) to synchronize data decoding on the receiving display.
• Consumer Electronics Control (Pin 13): The CEC line facilitates device control commands across interconnected hardware, allowing a single remote control to operate multiple connected units.
• Reserved / Utility (Pin 14): In early HDMI revisions, this pin was reserved. In HDMI 1.4 and later standards, it serves as the Utility line, often paired with the Hot Plug Detect line to carry the HDMI Ethernet Channel (HEC) and Audio Return Channel (ARC/eARC).
• DDC Bus (Pins 15 & 16): The Display Data Channel clock (SCL, Pin 15) and data (SDA, Pin 16) lines operate on an I2C protocol, enabling the source device to read Extended Display Identification Data (EDID) and manage HDCP content protection handshakes.
• DDC/CEC Ground (Pin 17): Provides a dedicated reference ground return line for the DDC, CEC, and Hot Plug lines.
• +5V Power Line (Pin 18): Supplies up to 55 mA of 5-volt direct current power from the source to power the display's EDID EEPROM chip when the display is in standby mode.
• Hot Plug Detect (Pin 19): Monitors electrical connection status, triggering the source device to initiate authentication and EDID handshakes when a display is plugged in.