USB power delivery
Choose the charging power you need.
The table below breaks down power delivery capacity of various USB connectors. Power ratings are listed as maximums due to a couple of reasons. First, a circuit will only conduct as much power as the receiving device needs. Second, power delivery can be limited by each component of the circuit, the supplying device, the receiving device, and the cable. It is safe to use a cable with a power rating that exceeds the source and destination device maximum ratings. A cable rated below the receiving device power rating can result in slow charging or not charging at all.
Be mindful that each cable has its own rating and might not reach the maximum listed in this table for the connector types used.
| Connector Type | Maximum Power Delivery | Notes |
| USB-A | 15W (5V/3A) typical | Legacy ports/cables rarely exceed this. No full USB PD support. |
| USB-B (standard) | 15W (5V/3A) typical | Limited by USB 2.0/BC specs. |
| Micro-USB (2.0) | 10–15W (5V/2–3A) | Supports Battery Charging (BC 1.2). Quick Charge possible on some devices. |
| Micro-USB (3.0 Superspeed) | 15W typical | Same power limits as standard Micro-USB. |
| Mini-USB | 10–15W (5V/2–3A) | Older standard; similar to Micro-USB limitations. |
| USB-C | Up to 240W (PD 3.1 EPR) | 60W standard for basic cables; 100W common; 140W/240W requires e-Marker chip. |
| Thunderbolt 3 / 4 (USB-C) | Up to 100W (typically) | Uses USB PD; many support 100W minimum. |
| Thunderbolt 5 (USB-C) | Up to 240W (PD 3.1) | Highest power + 80–120 Gbps data. |
defining power
Watts, Amps, and Volts
Power, measured in Watts, is a measurement of how much energy is being used in an electrical circuit. Power in our direct current (as opposed to alternating current) USB cables can be calculated as the Volts of voltage multiplied by the Amps (short for Amperes) of current. For example, a typical USB-A cable delivering 5 Volts of potential difference at a maximum current flow of 3 Amperes is supplying 15 Watts of power.
ELECTRONIC MARKER
How does USB know power ratings?
e-Marker (short for Electronic Marker) is a small integrated circuit (chip) embedded inside certain USB-C cables that actively communicates the cable’s certified power-carrying capabilities to connected devices and chargers. Using the USB Power Delivery (PD) protocol over the Configuration Channel (CC) wires, the e-Marker tells the devices the cable’s maximum safe current and supported voltage levels. This enables safe negotiation of higher power levels beyond 60 Watts, such as 100W, 140W, or 240W. Cables that typically include an e-Marker are those rated for 100W or higher, including most 100W+ USB-C charging cables, Thunderbolt 3/4/5 cables, USB4 cables, and high-performance USB-C to USB-C cables designed for fast charging of laptops, workstations, and high-power devices. Basic 60W or lower USB-C cables usually do not need one. This smart communication is a key reason modern USB-C cables are much safer and more capable than older USB standards.