Find the busiest hour on a busy day in your call log. Count every call that came in, answered or not.
Include the time spent writing notes or booking after the caller hangs up.
How long you are willing to let a caller wait for a person.
Call centers often aim for 80% of calls within 20 seconds. Pick what your callers will put up with.
Your guess. Breaks, lunch, and other work like checking people in. Leave at 0% to count only time on the phone.
People answering phones in your busiest hour
3
Your calls add up to 80 minutes of talking, packed into one hour. With 3 people, 84.2% of callers are answered within 20 seconds, the average wait is 26 sec, and 18% of callers wait at all.
| People | In 20 sec | Avg wait | Busy |
|---|---|---|---|
| 2 | 49.5% | 3 min 12 sec | 67% |
| 3 | 84.2% | 26 sec | 44% |
| 4 | 95.8% | 5 sec | 33% |
| 5 | 99% | 1 sec | 27% |
Schedule 3 people for that hour. If they take breaks or do other work, raise the time away slider.
20 calls × 4 min ÷ 60 = 1.33 hours of calls an hour. Erlang C turns that into the chance a caller waits, then the share answered in time and the average wait for each number of people. It assumes calls arrive at random and callers wait instead of hanging up, so treat the answer as the least you need.
Start with Small TalkCalls bunch up, so one person is rarely enough
Ten calls an hour sounds easy for one person. If each call takes three minutes, that is only half an hour of talking. But calls do not wait their turn. Two come in a minute apart, then nothing for twenty minutes. Every time they bunch up, the second caller waits on hold or hangs up.
Call centers size their teams with a formula called Erlang C. It takes the calls in your busiest hour, how long each call lasts, and how fast you want them answered, and gives the fewest people who can hit that target. This calculator runs the same math on your own numbers.
You also see the average wait, the chance a caller waits at all, and how busy each person would be, so you can weigh a short wait against paying people to sit by the phone.
How to use the call staffing calculator
1
Find your busiest hour
Open your call log and find the hour with the most calls on a busy day. Count every call, including the ones nobody answered.
2
Time your calls
Use the average call length from your call log, then add the minute or two spent writing notes or booking after the caller hangs up.
3
Set your answer target
Pick how many seconds a caller should wait at most and the share of calls that should meet it. Then read how many people you need.
What Erlang C is, in plain words
Erlang C is a formula a Danish telephone engineer, A. K. Erlang, worked out more than a hundred years ago. Call centers still use it to plan staff. You give it the calls in an hour, how long each one lasts, and the number of people answering. It tells you the chance a caller has to wait, the average wait, and the share of calls answered within your target.
Why one person cannot keep up
Take 10 calls an hour at 3 minutes each. That is 30 minutes of talking, so one person is free half the hour. But calls arrive at random and bunch up, so about half of callers find the line busy, and the average wait across all callers works out to 3 minutes. A second person brings the average wait down to about 12 seconds.
What the math assumes
Erlang C assumes calls arrive at random, every caller waits in line instead of hanging up, and every person can take any call. Real callers hang up or go to voicemail when the wait runs long, and calls can bunch up inside the hour, around opening time or lunch. Each hang-up is a caller you lost, so treat the answer as the least you need, not a comfortable number.
How the math works
Calls an hour times call length in hours gives your traffic in erlangs. One erlang is one person on the phone for the whole hour. With more people than erlangs, Erlang C gives the chance a caller waits. The share answered in time is 1 minus that chance times e to the power of minus (people minus erlangs) times your target seconds over call length in seconds. The average wait is that chance times call length over (people minus erlangs). The calculator adds one person at a time until your target is met, then divides by 1 minus your time away to get people to schedule.
Or let FrontDesk Talk handle it
Your busiest hour, with no line
FrontDesk Talk answers up to 10 calls at once, so a rush of calls doesn’t leave callers on hold. Every call gets picked up on the first ring, 24/7, with a Talk Note after each one. Small Talk is $99 a month with no contract.
Questions
How many receptionists do I need for 100 calls a day?
It depends on when those calls come in, not the daily total. 100 calls spread evenly over 10 hours is 10 an hour, but calls rarely spread evenly. Find your busiest hour in your call log and enter that. If you only know the daily total, divide by your open hours for an average hour, then try higher numbers to see what a rush does.
What is a good answer time target?
A target often used by call centers is 80% of calls answered within 20 seconds. For a small business, think about who is calling. Someone with a burst pipe or a sick child will not wait long, so a short target makes sense. Try a few targets and see how many people each one takes.
What is time away from the phone?
Call centers call it shrinkage. It is paid time when a person is not free to answer: breaks, lunch, meetings, training, and other work like checking people in or taking payments. If you set 25%, the calculator schedules enough people that the ones left on the phone still meet your target.
Why does adding one person change the wait so much?
When everyone is busy most of the hour, there is no slack to absorb a bunch of calls, so the line grows fast. One more person adds that slack. At 10 calls an hour of 3 minutes each, going from one person to two cuts the average wait from 3 minutes to about 12 seconds. Past that point, each extra person helps less.
Can an AI receptionist handle several calls at once?
Yes. FrontDesk Talk takes up to 10 calls at the same time for each business, so callers do not wait in line for someone to get free. If your busiest hour needs more than 10 lines, the calculator tells you. It answers on the first ring, 24/7, and transfers urgent calls to your cell. You get a Talk Note after every call.
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