This calculator implements the Erlang B Traffic Model for Telephone Systems design, allowing to estimate the blocking figure for a central office exchange or a PABX.


The inputs are: the traffic value in Erlangs and the number of lines. The result is the blocking figure.

Traffic (Erlangs):
Number of lines (N) :
Blocking (B) : %


obs.: Use the dot format (0.0) for decimal numbers.




A central office exchange, that within the busiest hour handles 1000 calls with average call duration of 3 minutes, presents a traffic of 50 Erlangs.


If this central office exchange has 60 lines, the blocking figure, or the probability of a call to be blocked is 2.16 %.




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