MOS and R-factor scale
| R-factor | MOS (approx.) | User satisfaction |
|---|---|---|
| 90–100 | 4.34–4.5 | Very satisfied |
| 80–89 | 4.03–4.33 | Satisfied |
| 70–79 | 3.60–4.02 | Some users dissatisfied |
| 60–69 | 3.10–3.59 | Many users dissatisfied |
| 50–59 | 2.58–3.09 | Nearly all users dissatisfied |
| < 50 | < 2.58 | Not recommended |
How this calculator works
It uses a widely published simplification of the ITU-T G.107 E-model for a G.711 call:
effective latency = latency + 2 × jitter + 10
R = 93.2 − effective/40 (effective < 160 ms)
R = 93.2 − (effective − 120)/10 (effective ≥ 160 ms)
R = R − 2.5 × packet loss %
MOS = 1 + 0.035R + 0.000007 × R × (R − 60) × (100 − R)It's an estimate for comparing networks, not a measured listening score. The full E-model also accounts for codec, echo, noise and loss patterns. Run any test on this site and your numbers will pre-fill above.
Frequently asked questions
What is a good MOS score for VoIP?
4.0 or higher is good business quality and 4.3 or higher is excellent. Between 3.6 and 4.0 some users notice impairment. Below 3.6 many callers are dissatisfied.
What is the highest possible MOS score?
The scale runs to 5, but real calls don't reach it. With the G.711 codec on a perfect network, the E-model gives an R-factor of about 93.2, which converts to a MOS of about 4.4. Wideband (HD) codecs can sound noticeably better than narrowband, but are scored on extended scales.
What is R-factor in VoIP?
R-factor is the 0–100 transmission rating produced by the ITU-T G.107 E-model. It starts from a best-case value and subtracts impairments for delay, equipment and codec, and packet loss. It converts to MOS with a standard formula.
How is MOS calculated?
Originally MOS was the average score a panel of listeners gave calls (ITU-T P.800). Network monitoring tools estimate it instead by calculating an R-factor from latency, jitter and packet loss and converting it to a 1–5 MOS.
Which affects MOS more: latency, jitter or packet loss?
In the simplified model, each 1% of packet loss costs 2.5 R points, while latency costs little until effective delay passes about 160 ms, after which it costs 1 R point per 10 ms. Jitter counts double toward effective latency. In practice, loss and jitter hurt most on typical business networks.
Why is my MOS low when my speed test is fast?
MOS doesn't depend on speed. A fast connection with high jitter, packet loss or latency under load still scores poorly. Run the Bufferbloat and Jitter tests to find which impairment is lowering the score.
Sources & references
- ITU-T G.107 — The E-model (R-factor)
- ITU-T P.800 — Methods for subjective determination of transmission quality (MOS)
- ITU-T G.114 — One-way transmission time
Written by Eric · Reviewed November 2026