Call Quality (MOS) Calculator
Implements the ITU-T G.107 E-model. "The calls sound bad" is not something a carrier will act on; an R-factor of 62 against a measured 180 ms of latency and 3% loss is.
Ie · Bpl — equipment impairment and packet-loss robustness (G.113)
Jitter is charged as buffer delay, not as its own impairment: a jitter buffer converts variance into latency, and it is that added latency the model sees. Effective one-way delay is taken as latency + 2 × jitter, the usual sizing for a buffer that absorbs most of the variance.
MOS
R-factor
Verdict
- Effective one-way delay
- Delay impairment (Id)
- Equipment + loss impairment (Ie-eff)
- Dominant factor
What the numbers mean
MOS is a 1–5 opinion scale; R is the 0–100 transmission rating it derives from.
- 4.3+ — indistinguishable from a landline. G.711 on a clean LAN.
- 4.0–4.3 — what a well-run SIP trunk should deliver. Nobody complains.
- 3.6–4.0 — noticeably compressed but perfectly usable. Typical G.729.
- 3.1–3.6 — users start reporting it. Expect "the line is not great".
- Below 3.1 — people ask each other to repeat themselves; below 2.6 they hang up and redial.
A MOS produced by a model is not the same as one produced by a listening panel — it is repeatable and arguable, which is what makes it useful in a fault report. Note the cliff at roughly 150–200 ms of one-way delay: below it people talk normally, above it they start colliding and taking turns.