How to find your MTU on Windows

Open Command Prompt and run netsh interface ipv4 show subinterfaces. The MTU column next to the adapter you play on is your current value. Most home connections show 1500. If you want to check what your line actually carries, use the ping test below.

Fastplay team · Updated

Why the scan asks for it

Windows cuts network traffic into packets no bigger than the MTU. If your line can't carry that size, packets get split or dropped and sent again. You feel that as ping spikes and rubber-banding, not as low frames.

Network settings only help when they're built around the size your connection really carries. Wrong number, and the tuning does nothing or makes it worse. That's why it's worth two minutes.

Check your current MTU

  1. Press the Windows key, type cmd and open Command Prompt. No admin needed.
  2. Run:
    netsh interface ipv4 show subinterfaces
  3. Find the row for the adapter you play on. On a cable it's usually called Ethernet, on wireless it's Wi-Fi.
  4. The number in the MTU column is your MTU. Ignore Loopback Pseudo-Interface 1, that one is always 4294967295 and means nothing here.

Example output (yours will differ):

   MTU  MediaSenseState   Bytes In  Bytes Out  Interface
------  ---------------  ---------  ---------  -------------
4294967295                1          0      48213  Loopback Pseudo-Interface 1
  1500                1  2487113024  184522871  Ethernet
  1500                5          0          0  Wi-Fi

A fitting ping replies like Reply from 1.1.1.1: bytes=1472 time=11ms TTL=58. Too big prints Packet needs to be fragmented but DF set.

Find the largest MTU your connection carries

This sends pings that aren't allowed to be split up, so you can see the biggest size that gets through.

  1. In the same Command Prompt, run:
    ping 1.1.1.1 -f -l 1472
    -f means "don't fragment", -l sets the payload size in bytes.
  2. If you get normal replies, 1472 fits. Your MTU is 1472 + 28 = 1500. Done.
  3. If you see "Packet needs to be fragmented but DF set.", lower the size by 10 and try again: 1462, 1452, and so on.
  4. Once one works, go back up 1 at a time until it fails. The last size that worked is your number.
  5. Add 28 to it. That's your MTU. Example: 1464 works, 1465 fails, so your MTU is 1492.

The 28 is the packet header (20 bytes IP plus 8 bytes ICMP), which ping doesn't count in -l.

What to type in the scan

Enter the full MTU, not the ping size. So 1500, not 1472. The field takes 576 to 9000. If you're unsure, leave it empty; it's optional.

Things that trip people up

Want to go further?

The steps above are the settings Windows and your driver show you, and they are worth doing either way. Underneath them is a deeper layer of Windows scheduling, input, network and storage behavior that the normal menus do not expose. That is what Fastplay builds for, from a team working on gaming regedit optimization since 2015, with modules developed and tested over years. See what each module does.

Run a free scan

FAQ

What is MTU?

The biggest packet your connection sends in one piece, in bytes. Anything larger gets split.

Is 1500 good?

It's the standard for Ethernet and most home internet. If 1500 passes the ping test, you're fine.

Why does my netsh value differ from the ping test?

netsh shows what Windows is set to. The ping test shows what actually gets through to the internet. Your router or provider can be lower.

Do I need admin rights?

No. Both commands work in a normal Command Prompt.

Keep reading