How do I test my real LAN file transfer speed?

Two ways: copy a large file and watch the throughput in Task Manager's Performance tab (Windows) or Activity Monitor's Network tab (Mac) for the true end-to-end speed, or run iperf3 between two machines to measure the network alone without disk speed getting in the way. Run both if a real copy is slow but iperf3 is fast — then the disk is the limit.

What is a normal transfer speed on gigabit Ethernet?

Roughly 90–115 MB/s for a real file copy on healthy wired gigabit. The nominal 1 Gbps equals about 125 MB/s of raw line rate, and protocol overhead plus disk speed bring the usable figure down. Consistently under ~60 MB/s on wired gigabit points to a cable, switch, or storage problem.

Why is my transfer slower than my internet speed test?

An internet speed test measures your link to a remote server; a LAN transfer is limited by the slowest local hop — often a 100 Mbps port, an old cable, a Wi-Fi leg, or a slow hard drive on one end. Test with iperf3 to separate the network from the disks and find which one is capping you.

LAN Speed Test — How to Measure Your Real File Transfer Speed

Why Measuring Matters

A network card that reports a 1 Gbps link speed does not guarantee 1 Gbps throughput. Real transfer speed is affected by cable quality, switch capacity, drive read/write speed, CPU overhead from encryption, and protocol efficiency. The only way to know what your network actually delivers is to measure it.

This guide covers three methods — from quickest to most accurate — for measuring LAN file transfer speed on Windows and Mac.

Method 1 — Task Manager During a Real Transfer (Windows)

The fastest way to get a real-world number is to watch Task Manager during an actual file transfer.

Start copying a large file (at least 1GB, ideally 5GB+) from one machine to another on your LAN — use File Explorer, a mapped drive, or any LAN tool
On either machine: press Ctrl + Shift + Esc → Performance tab → select Ethernet or WiFi
Watch the "Send" and "Receive" values while the transfer is in progress

Read the throughput in Mbps shown on the graph, or calculate: transfer speed shown in MB/s × 8 = Mbps.

What you are looking for:

Wired Gigabit: 800–950 Mbps (~100–115 MB/s)
WiFi 5 (good conditions): 150–400 Mbps
If consistently below 200 Mbps on wired gigabit: there is a bottleneck

Limitation of this method: You are measuring the combined throughput of network + drive. If the drive is the bottleneck, the network measurement will be artificially low.

Method 2 — Activity Monitor During a Transfer (Mac)

Start a large file transfer over the network (Finder → Connect to Server, or AirDrop, or LocalSend)
Open Activity Monitor: Spotlight (Cmd+Space) → type Activity Monitor → Network tab
Watch "Data received/sec" or "Data sent/sec" depending on whether you are receiving or sending

Alternatively: System Settings → Network → [your connection] shows the current link speed (confirming 1 Gbps link, not actual throughput).

For actual throughput on Mac, the Activity Monitor method during a large transfer is the clearest real-world measurement.

Method 3 — iperf3 (Network-Only Measurement, Windows + Mac)

iperf3 is a free, open-source network benchmarking tool that measures pure network throughput without drive I/O as a variable. It sends test data directly between two machines in memory, isolating the network performance.

Install iperf3:

Windows: download from iperf.fr → no installation needed, run from a folder
Mac: install via Homebrew: brew install iperf3
Linux: sudo apt install iperf3

Run the test: On the machine that will receive (the server):

iperf3 -s

On the machine that will send (the client):

iperf3 -c [SERVER-IP-ADDRESS]

Replace [SERVER-IP-ADDRESS] with the LAN IP of the server machine (find it in Windows: Settings → Network → your connection → shows IPv4 address. On Mac: System Settings → Network → Details → IP Address).

Read the result: iperf3 reports throughput in Mbits/sec at the end of the test. Divide by 8 to get MB/s.

Expected results:

Wired Gigabit: 920–960 Mbits/sec
WiFi 5 (close to AP): 150–400 Mbits/sec
WiFi 6: 300–700 Mbits/sec

If your wired result is significantly below 900 Mbits/sec: Check cable, switch port, and NIC link speed.

Method 4 — Windows Built-In Network Test

For a quick sanity check without installing anything:

Open PowerShell as Administrator and run:

Test-NetConnection -ComputerName [HOSTNAME-OR-IP] -Port 445

This confirms the TCP connection to the SMB port is working. It does not measure throughput but confirms reachability and that SMB is not blocked by firewall.

Method 5 — LAN Speed Test Tool (Windows GUI)

LAN Speed Test (Totusoft) is a free GUI application for Windows that measures LAN throughput by writing and reading a test file across the network. It combines network and storage measurements and gives a clear MB/s result in a simple interface.

Download from totusoft.com
Run the application
Set the test file path to a mapped network drive or a UNC path (e.g., \\SERVERNAME\Share\)
Set test file size to 1GB or larger
Click Start

The result shows write speed (your machine writing to the remote share) and read speed (reading back). This reflects real-world file transfer performance including drive I/O.

Interpreting Your Results

Measured speed	Likely cause	Action
90–115 MB/s (wired)	Healthy gigabit LAN	No action needed
40–80 MB/s (wired)	Bad cable, wrong MTU, 100Mbps link	Check cable, confirm gigabit link
10–12 MB/s (wired)	Fast Ethernet (100 Mbps) link negotiated	Replace cable, check switch port
30–80 MB/s (WiFi)	Normal WiFi 5 conditions	Acceptable; wire for critical transfers
Under 10 MB/s (wired)	SMB encryption overhead, drive bottleneck, antivirus	Check each variable

Tools That Help With LAN Speed

For daily large file transfers, application-layer tools like Oxolan and LocalSend provide their own progress indicators showing current transfer speed in MB/s — giving you a real-world speed measurement as part of normal use.

Get Oxolan for Windows