How jitter is measured
Jitter is calculated by comparing consecutive ping measurements and averaging the differences between them. If your ping readings over a few seconds are 22, 24, 21, 23, 22 ms, the variation between consecutive readings is small — low jitter. If the readings are 15, 45, 12, 80, 20 ms, the swings are large — high jitter.
SpeedFast reports jitter alongside ping, giving you both the average delay and how stable that delay is.
What causes jitter
Network congestion is the most common cause — when packets compete for space on a congested link, some get delayed more than others. Wi-Fi interference (especially on the crowded 2.4 GHz band) adds unpredictable delays. Bufferbloat in your router can cause jitter to spike under load. Poor-quality network hardware, VPNs adding variable routing, and ISP-level congestion during peak hours all contribute.
What is acceptable jitter?
For most real-time applications:
| Jitter | Rating | Impact |
|---|---|---|
| < 5 ms | Excellent | Imperceptible — smooth video calls and gaming |
| 5–15 ms | Good | Minimal impact on most real-time activities |
| 15–30 ms | Acceptable | Occasional glitches in video/audio possible |
| > 30 ms | Poor | Noticeable audio/video disruptions, gaming stutter |
Why jitter matters more than you think
Most people focus on download speed and ignore jitter entirely. But real-time protocols (VoIP, video conferencing, gaming netcode) depend on packets arriving at predictable intervals. When jitter is high, the receiving device has to buffer incoming packets longer to smooth out the variation, which adds perceived latency — or drops packets entirely, causing skips and freezes.
If your speed test results show good download and low ping but your video calls still stutter, check jitter. It's often the hidden culprit.
Measure your jitter now to see whether your connection is consistent enough for what you need.