Adherence is the share of scheduled time agents spend doing what the schedule says, such as being on the phones when planned. Service level is the share of calls answered within a set time, for example 80% in 20 seconds. Enter your queue to see the service level an Erlang C queueing model gives at today's adherence and at each point lost, the agents it takes to hold your target, and what the overtime costs.
Every formula and assumption is in the published method.
Target 80%, met
Of 100 at 92% adherence
Agents on the queue
$129,180 a year to hold target
| Adherence | On the queue | Service level | Speed of answer | Target | To schedule | Overtime to hold target |
|---|---|---|---|---|---|---|
| 92% (today) | 92 | 88.5% | 7s | Met | 98 | None |
| 91% (-1) | 91 | 85.4% | 10s | Met | 99 | None |
| 90% (-2) | 90 | 81.5% | 13s | Met | 100 | None |
| 89% (-3) | 89 | 76.7% | 18s | Missed | 102 | $129,180 |
| 88% (-4) | 88 | 70.8% | 24s | Missed | 103 | $193,770 |
| 87% (-5) | 87 | 63.7% | 35s | Missed | 104 | $258,360 |
| 85% (-7) | 85 | 44.7% | 78s | Missed | 106 | $387,540 |
| 82% (-10) | 82 | 0.0% | overloaded | Missed | 110 | $645,900 |
At 92% adherence, 92 of 100 scheduled agents are on the queue. Erlang C (the standard queueing formula for how many callers wait, given calls, handle time and agents) gives 88.5% answered within 20 seconds (target 80%, met) and an average speed of answer (how long a caller waits before an agent picks up) of 7s.
Holding 80% within 20 seconds takes 90 agents on the queue. Service level first falls below target at 89% adherence (3 points lower), where it is 76.7%. That is how much adherence slack you have before callers start to feel it.
At 89% adherence, holding the target means scheduling 102 agents, 2 more than the roster: about 4,000 overtime hours, $129,180 a year at 1.5 × $21.53 an hour.
Overtime assumes the 820 calls an hour hold across 8 open hours a day and 250 days a year. Erlang C assumes every caller waits until answered. In practice some callers hang up, which removes them from the queue, so the service level you measure will run higher than this model shows.
Adherence is taken as the share of scheduled agents on the queue at any moment.
Overtime multiplier 1.5x, the US Fair Labor Standards Act minimum; hourly rate is the BLS median for customer service representatives, May 2025.
The call rate is taken to hold across 8 open hours a day and 250 days a year.
Published figures to hold your result against. Each measures something slightly different, so read what it counts before you compare. None of them changes your result or its grade.
Targets from practice. No public survey reports the adherence centers achieve.
The common target is a convention. A few regulators set their own standard for the centers they oversee.
SQM Group, 19 Jan 2023. What Are the Industry Standards for the Top Call Center KPIs?The US Bureau of Labor Statistics median for customer service representatives, May 2025. The tool opens at the national median; if you know your own pay, enter it in the tool.
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Method 1.1, published 28 September 2026. How this is calculated
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$129,180 a year to hold target