Latency, jitter and packet loss: how to measure them at home
Speed tells you how much data fits through the connection. Latency, jitter and packet loss tell you how smoothly it flows, and they're what decide whether a call freezes or a game lags.
In short
- Latency (ping) is the time for a round trip, jitter is how much it varies, packet loss is the share that never arrives. Calls and games depend on these more than on speed.
- Common references for voice: one-way delay under 150 ms, jitter under 30 ms, loss under 1%. Across your own Wi-Fi, to the router, a few milliseconds is normal.
- Ping the router and then an internet server. If the router is already slow or jumpy, the problem is your Wi-Fi; if only the server is, it's the line.
- If latency explodes only while something uploads or downloads, the line is saturated (bufferbloat), and a router setting can fix it.
On this page
A connection can be fast and still bad. A speed test that shows 300 Mbps says nothing about whether a video call will freeze every thirty seconds or whether a game will lag at the worst moment. Those depend on three other numbers, and you can measure all three at home.
What the three numbers mean
Latency, usually shown as ping, is the time a small message takes to reach a destination and come back, in milliseconds.
Jitter is how much that time changes from one message to the next. A steady 40 ms is fine for a call; a connection that swings between 10 and 120 ms is not, even if its average looks good.
Packet loss is the share of messages that never arrive. Each lost packet is a missing piece of voice, a frozen video frame or a game action that didn't register.
For speed, more is better. For these three, less is better, and steady matters as much as low.
What values to aim for
The reference most often quoted for voice comes from network design practice, used for example by Cisco: one-way delay under 150 ms, jitter under 30 ms and packet loss under 1%. Above those, people start talking over each other, voices break up and video freezes. Online games are more demanding about delay; most players feel the difference well before 100 ms.
Those figures are for the whole journey, from your device to the other person or the game server. The part inside your home, from the device to the router, should be a tiny slice of it. On a healthy Wi-Fi link a round trip to the router takes a few milliseconds and barely varies. If that short hop alone takes tens of milliseconds, or jumps around, the Wi-Fi is the problem.
Find out which part is to blame
The trick is to measure two things separately: your Wi-Fi, and the internet beyond it.
From a computer, open Terminal on a Mac or Command Prompt on Windows and ping your router, which is usually 192.168.1.1 or 192.168.0.1; the router's label or its app tells you the exact address. Let it run for a minute:
ping 192.168.1.1
Then ping a server on the internet, for example ping 1.1.1.1, for another minute. Compare the two.
- Router fast and steady, internet slow or jumpy: your Wi-Fi is fine. The line, the provider or the route to that server is responsible.
- Router already slow, jumpy or losing packets: the Wi-Fi link is the problem. Move closer to the router and try again; if it improves, it's coverage.
- Both fine, but calls still break: look at what else uses the connection while you're on the call, and read on.
On an iPhone, most speed test apps show ping and jitter to their server, which covers the whole route. Run the test next to the router and then in the room where the problem happens: if the numbers only get worse in the room, the Wi-Fi is the difference. Apps that measure the router specifically, including ours, show the Wi-Fi part on its own.
When latency explodes during uploads
There's one cause that catches many people out. When someone at home uploads a large file, backs up photos to the cloud or downloads a big game, the internet line fills up. Many routers and modems then hold data in long queues, and every other message has to wait behind it. Latency that was 20 ms can climb to several hundred, and calls and games collapse, while a normal speed test looks perfect.
This is called bufferbloat, and you can test for it. Some speed tests report latency "under load" or "loaded latency" alongside the idle ping; dedicated bufferbloat tests grade it directly. If latency jumps a lot only while the test is downloading or uploading, that's your answer.
The fix is in the router, not the Wi-Fi: a setting usually called QoS, Smart Queue Management or SQM, which keeps the queues short by limiting the line to slightly below its real speed. Not every provider's router has it; many third-party routers do.
What causes jitter and loss on the Wi-Fi itself
When the signal is weak, Wi-Fi resends data that didn't get through, and every resend adds delay. That's why jitter and loss rise in far rooms before the speed collapses. The fix is coverage: a better router position, a mesh node or an access point closer to the room. See Wi-Fi not reaching one room.
When the air is crowded, devices wait their turn to transmit, and the waits vary. Moving devices that support it to 5 GHz, where there's more room, usually steadies things. See 2.4 or 5 GHz.
And for anything where every millisecond counts, like a console or a desktop used for competitive games or important calls, an Ethernet cable takes the Wi-Fi out of the picture entirely: no resends, no queues for the air, a steady few milliseconds to the router.