Networking · DNS & connectivity
Latency, jitter, and what ping actually measures
A ping test gives you four numbers per packet: time-to-live, round-trip time, sequence number, and whether the packet was lost. The number most people care about is the round-trip time, but the others tell you different things about your connection. This post walks through what each one means.
TL;DR
Ping is round-trip time in milliseconds. Jitter is the variation. Packet loss is the percentage that never arrived. Here is how to read a ping test.
Round-trip time (RTT)
RTT is the milliseconds between sending a packet and getting the response. It includes the time for the packet to travel to the destination, the destination to process it, and the response to travel back. Lower is better. A typical home connection has 10–80 ms RTT to nearby servers and hundreds of seconds away. The speed of light is the floor — you cannot get lower than ~3.3 ms per 1000 km of fiber.
Jitter
Jitter is the variation in RTT across packets. If you send 50 pings and get 10ms, 12ms, 9ms, 11ms, 13ms, the average is 11ms and the jitter is about 2ms. High jitter means the network is unpredictable — packets are taking different routes or hitting congestion. Real-time applications (VoIP, video calls, gaming) are much more sensitive to jitter than to average RTT, because a sudden 50ms spike can cause a glitch even if the average is 20ms.
Packet loss
Packet loss is the percentage of sent packets that never got a response. 0% is ideal. 1% is noticeable for real-time applications. 5%+ means your connection has a serious issue. Packet loss can be transient (one bad burst, then fine), persistent (regularly losing 1–2%), or total (the destination is unreachable). The cause is usually either congestion (router buffers are full, packets are dropped) or a faulty physical link.
What a multi-server test shows
A single ping tells you the latency to one server, from your network, right now. A multi-server test (like the one on /ping/) sends the same query to 9 geographically diverse servers and shows the latency to each. The pattern is informative: if latency is low everywhere, your connection is fast. If one region is consistently slower, that region is geographically far from you. If results vary wildly across runs, your connection has jitter or packet loss.
Try it →
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