The score ranges from 1 to 5, with a theoretical maximum of 4.4 (because of overhead caused by codecs used to encapsulate voice over the wire). It is calculated by average latency, average jitter, and packet loss.
A = (latency + jitter) * 2
If A < 160 then B = 93.2 - ( A / 40 )
If A >= 160 then B = 93.2 - ( A - 120 ) / 10
C = B - ( packet loss * 2.5 )MOS = 1 + (0.035) * C + (.000007) * C * (C-60) * (100-C)
A MOS score above 4.0 should support most VoIP applications, provided the bandwidth is also available.