# MOS
> Mean Opinion Score – a 1–5 rating scale for perceived voice call quality

MOS (Mean Opinion Score) rates perceived voice quality on a 1-to-5 scale.

## What is MOS?
Mean Opinion Score (MOS) is a standardized measure of voice call quality, rated on a scale from 1 (bad) to 5 (excellent). Originally based on human listener panels, MOS is now often calculated algorithmically using tools like PESQ or POLQA.

## MOS thresholds for VoIP
A MOS of 4.0+ is considered toll quality. Scores between 3.5 and 4.0 are acceptable for business use. Below 3.0, users typically perceive noticeable degradation. Factors affecting MOS include [codec](/voip-glossary/codec/) choice, [jitter](/voip-glossary/jitter/), [latency](/voip-glossary/latency/), and packet loss.

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