# Latency
> The time delay between sending and receiving voice data over a network

Latency is the round-trip delay in voice data transmission, directly impacting VoIP call quality.

## What is latency?
Latency (also called delay) is the time it takes for a voice packet to travel from the sender to the receiver. In VoIP, latency is typically measured as one-way delay. Calls feel natural when one-way latency stays below 150 ms; above 300 ms, conversations become noticeably awkward.

## Causes of latency
Sources include network propagation delay, codec processing time, [jitter](/voip-glossary/jitter/) buffer delay, and queuing delays in routers. Geographic distance, congested links, and poorly configured [QoS](/voip-glossary/qos/) policies all contribute.

## Related Terms
- [Jitter](/voip-glossary/jitter/)
- [QoS](/voip-glossary/qos/)