Check LAN speed: distinguish link rate, file copying and internet

Windows shows 1 Gbit/s, but a file copies slowly? The indicator describes the negotiated connection to the next network device. It measures neither the whole path to your NAS nor your internet connection. These Windows 11 steps separate the measurements and produce useful comparisons.

Read the link rate

Open Windows PowerShell and run this read-only command:

Get-NetAdapter -Physical | Select-Object Name, Status, LinkSpeed

Find the Ethernet adapter actually in use with status Up. Do not assess Wi-Fi or another port instead. A reading of 100 Mbit/s rather than the expected 1 Gbit/s is a reason to check both ports’ capabilities, cables, connectors and intermediate adapters. Change only one cable or an approved port at a time and read the value again. Do not simply force speed or duplex mode.

Compare bits and bytes correctly

One byte contains eight bits: 1 Gbit/s mathematically equals 125 MB/s before protocol overhead. At 100 Mbit/s it is 12.5 MB/s. These are not guaranteed file copy rates. Programs may also display MiB/s instead of decimal MB/s. About 110 MB/s is plausible for an ordinary single gigabit SMB connection under favorable conditions; slower storage, CPU, load and protocol features can reduce this substantially.

Measure a local copy carefully

  1. Use your own PC and an authorized test share on your own NAS or second PC, preferably both connected by Ethernet to the same switch. Record the whole path, including any dock, powerline link or Wi-Fi bridge.
  2. Choose an existing, nonconfidential large file, such as a video several gigabytes in size. Check free space at the destination. Copy, do not move, into a new test folder without existing files of the same name.
  3. Record file size and total time to completion, not just the initial peak. Repeat and test the opposite direction with a different test destination. Caches may speed up repeated tests; record the sequence.
  4. Then compare a folder containing many small files separately. More file operations often mean far fewer MB/s without a faulty cable.

This test measures file transfer including storage, SMB and endpoints, not just the wire. Keep security features such as SMB signing, encryption and antivirus enabled. A faster switch cannot fix a storage bottleneck.

Test internet separately

A browser speed test also includes the router, provider connection, internet path and test server. Record server, time, download/upload and units. Avoid simultaneous downloads or backups you control for comparison; do not independently disable required corporate VPNs. Repeat under the same conditions. Good local throughput with slow internet does not prove a provider fault, but points further investigation toward a different path.

Document the result

Record adapter link rates, both endpoints, connection path, file type, size, time and direction. Compare only measurements made under the same conditions. Then change one component deliberately and repeat the appropriate test instead of altering several network settings at once.

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