Latency is a delay or lag that occurs on computer networks. In voice communications or VoIP (Voice over Internet Protocol), latency refers to the time between when a voice packet is sent and when it reaches its destination. High latency translates to a delay or echo caused by slow network connections.

Latency is measured in milliseconds (ms), which are thousandths of a second. A latency of 20 ms is normal for VoIP calls; a latency of 150 ms is barely noticeable and therefore acceptable. Anything higher than that, however, and the quality starts to degrade. At 300 ms or higher, latency becomes unacceptable.

Latency is measured in two ways:

The negative effects of latency on call quality include: