How the calculation works

Coverage. Hours to cover a year = hours per day × days per week × 365 ÷ 7, so 24×7 is 8,760 hours and 16×5 is 4,171.4.

Productive hours per engineer = paid hours per week × 52 − days off × (paid hours per week ÷ 5), where days off = PTO + holidays + training + sick days. The defaults (40 hours; 15, 10, 10 and 5 days) give 1,760 hours a year. They are planning assumptions with no published source; replace them with your own policy.

Engineers per position = coverage hours ÷ productive hours; coverage FTE = positions on duty × engineers per position.

Event workload (optional). Hours a year = events per day × minutes per event ÷ 60 × days covered a year. Workload FTE = those hours ÷ (productive hours × the share of time on event work, 70% by default). Events are assumed to arrive while the NOC is staffed and spread over the day; a major outage that ties up the whole shift is not modeled.

L1 engineers = the larger of coverage FTE and workload FTE, rounded up. L2 and L3 = L1 ÷ the ratio you enter, rounded up; they are headcount, not extra positions on the night shift. Annual cost = headcount × the loaded cost you enter, if any.

Worked example

A 24×7 NOC with one engineer on duty and the default time off, handling 60 events a day that need about 20 minutes of hands-on work each, with one L2 engineer per three L1:

  • Engineers per position: 8,760 ÷ 1,760 = 4.98, so coverage needs 4.98 FTE
  • Event work: 60 × 20 min = 20 hours a day × 365 = 7,300 hours a year ÷ 1,232 = 5.93 FTE, a little over one engineer on duty on average
  • The workload is larger, so 6 L1 engineers; L2: 6 ÷ 3 = 2
  • Total: 8 people

At 20 hours of event work a day, one engineer on duty is busier than the 70% share allows, so the sixth L1 engineer covers the excess across shifts. A second position on duty would raise coverage to 9.95 FTE and 10 L1 engineers.

Staffed, on-call or managed

A NOC doesn’t have to be staffed every hour. Common setups are a staffed day shift with an on-call engineer at night, a follow-the-sun team across time zones, or a managed NOC that watches the network around the clock and escalates to your team. The downtime cost calculator puts a number on how fast an outage needs a person on it, which decides how much staffed coverage is worth paying for.