Erlang C calculator

Classic staffing calculation. Tells you how many agents are needed to meet a service-level target. Runs entirely in your browser — nothing is sent anywhere.

Inputs

Contacts in interval

Number of calls/contacts arriving during the interval below.

Interval length (minutes)

Average handle time (seconds)

AHT = talk time + after-call work, in seconds.

Target service level (%)

Target answer time (seconds)

e.g. “80% in 20 seconds” → SL 80%, time 20s.

Max occupancy (%) — optional

A cap to keep agent utilisation sustainable. Leave high (e.g. 95) to ignore.

Shrinkage (%) — optional

Used to gross net agents up to scheduled headcount.

Results

Agents required (net)—

Scheduled (after shrinkage)—

Achieved service level—

Average speed of answer—

Occupancy—

Probability of waiting—

Offered load (Erlangs)—

Sensitivity

Agents	SL %	ASA (s)	Occ %

Erlang C assumes Poisson arrivals, exponential handle times, infinite queue and infinite patience, and a single skill. Real contact centres rarely satisfy these assumptions perfectly — treat Erlang C as a planning baseline, not a precise prediction. If abandonment matters, use Erlang A instead.