USB-C to Gigabit Ethernet Adapter: The Chain to 940 Mbps
Gigabit is a chain of four links, and the slowest one decides the result. Checking each in order is faster than blaming the adapter.
Quick Answer
| Link | Requirement | Check |
|---|---|---|
| Adapter controller | Gigabit rating | Specification |
| USB-C link | Data capable, USB 3 class | Port specification |
| Patch cable | Cat5e or better, undamaged | Negotiated speed |
| Switch port | Gigabit | Router or switch interface |
Expect about 940 Mbps, or roughly 110 MB/s on a bulk file transfer.
Verifying Each Link
Negotiated speed first
The operating system reports what the adapter and switch agreed. 100 Mbps means one end cannot do better.
Cable second
A damaged pair drops the link to 100 Mbps rather than failing outright.
Port third
A USB 2.0 class link caps throughput at 300 to 400 Mbps.
Switch last
An old 100 Mbps port limits everything downstream of it.
Getting the Last Few Percent
- Connect the adapter directly to the host, not through a hub.
- Disable USB selective suspend for the interface.
- Use a known good Cat5e or Cat6 patch.
- Enable jumbo frames only if every device supports them.
- Measure with a bulk transfer, not a speed test site.
Real-World Applications
- NAS access where wireless is too slow.
- Overnight backups across a wired network.
- Media workstations pulling footage.
- Workstations with a failed onboard port.
Related Guides
For 2.5 GbE models, read USB-C to 2.5 Gbps. For adapter variants, see USB-C network adapter. For cable choice, start with USB-C to Cat6.
FAQ
Why do I only get 300 Mbps?
The host port is likely USB 2.0 class.
Why 100 Mbps?
A damaged cable, a 100 Mbps switch port, or a 100 Mbps adapter.
Is 940 Mbps really the limit?
Yes. Protocol overhead means gigabit delivers about 940 Mbps of payload.
Does the adapter need its own power?
No. It draws a small amount from the host port.