VoIP Jitter and Latency Explained (And How to Reduce Them)

Latency is the delay between someone speaking and the other person hearing it. Jitter is the variation in that delay from one moment to the next, rather than the delay itself. A call can have consistent latency and still sound perfectly clear, but inconsistent latency — jitter — is what makes audio sound choppy, robotic, or out of sync, even when the connection isn't actually slow.

What Is Latency?

Latency is simply the time it takes for your voice to travel from your device to the other person's, measured in milliseconds. Every network connection has some latency — it's physically impossible to send data with zero delay — but the amount matters a great deal for a real-time conversation like a phone call.

A small, consistent amount of latency is barely noticeable. Above a certain point, people start talking over each other without realising it, because the natural pauses in conversation get thrown off by the delay.

What Is Jitter?

Jitter is the inconsistency in that delay. If latency is the length of a queue, jitter is how unpredictably fast or slow that queue moves. Voice data travels across the internet in small packets, and if those packets don't arrive at a steady, even pace, the audio has to be reassembled unevenly at the other end — which is what creates that choppy, glitchy sound, even if the average delay isn't particularly high.

VoIP systems use something called a jitter buffer to smooth this out, briefly holding onto early-arriving packets so they can be played back at a steady rate. A jitter buffer helps up to a point, but it can't fully compensate for a genuinely unstable connection.

How Are Jitter and Latency Different from Packet Loss?

These three terms often get used interchangeably, but they describe different problems:

• Latency — how long data takes to arrive
• Jitter — how much that arrival time varies
• Packet loss — data that doesn't arrive at all

A call can suffer from any one of these independently, though in practice a poor connection often shows symptoms of more than one at once.

What Causes Jitter and Latency on a VoIP Call?

• Network congestion — too much other traffic competing for the same connection
• Wi-Fi instead of a wired connection — inherently less consistent than ethernet
• Long physical distance — calls routing internationally naturally carry more latency than local ones
• Underpowered or outdated routers — struggling to process traffic quickly and consistently
• No Quality of Service (QoS) prioritisation — voice traffic competing on equal terms with everything else on the network

What Are Acceptable Levels for VoIP?

As a general guide, one-way latency under 150 milliseconds is considered good for voice calls, with quality noticeably degrading as it climbs toward 300 milliseconds and above. Jitter ideally stays under around 30 milliseconds — the lower, the better — since even small amounts of variation can be audible on a call in a way that a similar amount of pure latency wouldn't be.

These aren't hard cutoffs so much as general thresholds where most people start to notice a real difference in call quality.

How to Reduce Jitter and Latency

• Use a wired connection instead of Wi-Fi wherever possible, particularly for anyone on calls regularly
• Set up Quality of Service (QoS) on your router so voice traffic is prioritised over other network activity
• Check for network congestion during problem periods — large uploads or video calls running alongside voice calls are common culprits
• Upgrade ageing network hardware, since older routers sometimes can't handle traffic prioritisation properly even when QoS is configured
• Consider a dedicated connection, such as a leased line, for businesses where call quality is genuinely business-critical and standard broadband isn't cutting it

Frequently Asked Questions

Can I test my own latency and jitter? Yes, various free online speed test tools report latency (sometimes called "ping") and jitter alongside download and upload speed, giving a rough sense of your connection's suitability for VoIP.

Does a faster broadband package automatically reduce jitter? Not necessarily. Jitter is about consistency, not raw speed, so a fast connection with inconsistent performance can still produce noticeable jitter, while a slower but stable connection sometimes performs better for voice calls specifically.

Is jitter worse on Wi-Fi than a wired connection? Generally yes, since Wi-Fi is more prone to interference and variable performance than a direct ethernet connection, which tends to be more consistent.

Is this the same issue as one-way audio? No. One-way audio is a routing problem, usually caused by NAT or firewall configuration, where audio fails to travel in one direction entirely. Jitter and latency affect the quality of audio that is flowing, rather than blocking it. Our guide to one-way audio covers that issue separately.

Understanding jitter and latency is the first step to fixing them — the second is checking your network properly. Request a quote if you'd like T2K to assess your setup, or read our guide to why VoIP calls break up for a wider troubleshooting checklist.