Auditor utilisation rate: how to measure it and what good looks like
How to calculate auditor utilisation rate, which days to count, what good looks like for a certification body and how to raise it without burning people out.
Auditor utilisation rate is the share of an auditor's available working days spent on chargeable audit work. Calculate it as chargeable audit days delivered divided by available days, times 100. Available days are contracted days minus leave, public holidays, training and planned non-audit duties. Most certification bodies should target a high but realistic rate, because travel, reporting and calibration also need time.
Key takeaways
- Utilisation is only comparable if everyone uses the same numerator and denominator, so write the definition down first.
- The denominator is available days: leave, training and non-audit duties come out.
- Published results show large gains are possible, such as one compliance and risk company moving from 74% to 85%.
- Low utilisation of internal auditors usually shows up as avoidable subcontracting, so track both together.
What is auditor utilisation rate?
Auditor utilisation rate tells you how much of your internal audit capacity turns into chargeable work. It is the most direct measure of whether your scheduling is using the people you already employ. A low rate means paid auditor days are going unused while, very often, the same work is sent to subcontractors.
The number is simple. The arguments start with what goes in the top and the bottom of the fraction. Two regional managers can both report 80% and mean completely different things, so agree one definition before you compare offices, teams or years.
Chargeable audit days delivered by an auditor in a period, divided by that auditor's available days in the same period, expressed as a percentage.
For a wider view of capacity across auditors, days and sites, see resource utilisation in certification bodies.
How to calculate auditor utilisation
Start with contracted days. Take out annual leave, public holidays, planned training, CPD, calibration meetings and any agreed non-audit duties such as technical review or certification decisions. What is left is available days. The savings calculator on this site assumes 200 working days per auditor per year (1,650 working hours), which is a reasonable starting point if you have no better figure.
Then count chargeable days: the audit days you invoice, as set by your audit time calculation. Include on-site and remote audit time and any chargeable off-site time. Leave out travel unless you invoice it as audit time.
| Definition | Numerator | Denominator | Use it for |
|---|---|---|---|
| On-site rate | Audit days at the client (on-site or remote) | Available days | Comparing auditors doing similar work |
| Chargeable rate | All invoiced audit days, including chargeable off-site time | Available days | Company KPI and pricing decisions |
| Committed rate | Chargeable days plus travel and unbilled reporting | Available days | Spotting overload and burnout risk |
Report the chargeable rate as your headline figure and the committed rate beside it. A high chargeable rate with a committed rate near 100% means auditors are working evenings to keep up. The audit man-day article explains how audit days are counted in the first place.
A worked example
A body employs 20 internal auditors. At 200 available days each, capacity is 4,000 days a year. Last year they delivered 3,000 chargeable days, so the chargeable utilisation rate is 3,000 divided by 4,000, which is 75%.
Raising that to 85% releases 400 chargeable days. That is the equivalent of two full-time auditors, found without hiring. If the body currently subcontracts work that its own auditors are competent to do, those 400 days can come straight back in-house.
- Fix the denominatorPull contracted days per auditor from HR and subtract leave, holidays, training and agreed non-audit roles.
- Fix the numeratorExport invoiced audit days per auditor from your certification system for the same period.
- Calculate per auditorDivide, then look at the spread. The average hides the auditors at 50% and the ones at 105%.
- Find the cause of gapsFor each low figure, check competence scope, home location and calendar gaps against the work you subcontracted.
Our guide to increasing utilisation before hiring covers the levers in more detail.
What is a good auditor utilisation rate?
There is no published industry benchmark that we can point to with confidence, and figures quoted without a definition are not comparable. The practical question is how close you can get to the ceiling your own rules allow. Travel time, report writing, witness observations, calibration and CPD all need room, so 100% is neither achievable nor desirable.
What we can show is what has happened in real certification bodies after they changed how they schedule. These are results from ScheduleAI customers, each measured on their own definition.
Control Union reached 92% internal team utilisation. Use these as evidence of what is possible, then set your own target from your own baseline and rules.
Why is auditor utilisation rate low?
In most bodies the usual cause is a mismatch between where the work is, what it needs and who is free. Planners allocate audit by audit, so they cannot see that a subcontractor booking in March was the day an internal auditor had spare.
MythLow utilisation means we have too many auditors.
RealityUsually it means the right auditor is not being matched to the right audit. Check how much competent work went to subcontractors before cutting headcount.
MythHigher utilisation always means more pressure on auditors.
RealityClustering audits geographically cuts travel, so auditors can deliver more chargeable days with fewer hours on the road.
MythA monthly average tells us enough.
RealityUtilisation is seasonal and uneven. Measure per auditor and per month, then look at the peaks and troughs.
Competence is the most common hidden constraint. An auditor with a narrow scope simply has fewer audits they can take. A clear auditor competence matrix shows where extending one IAF code would open up the most work.
How to raise utilisation this quarter
You do not need new systems to start. You need visibility of three things at once: open demand, internal free days and competence. Put them side by side and the gaps become obvious.
- ✓Agree and publish one written definition of utilisation for the whole company
- ✓Report utilisation per auditor per month as well as the company average
- ✓List every subcontracted audit from last quarter and check whether a competent internal auditor was free
- ✓Plan audits in batches across a month or quarter, not one at a time
- ✓Cluster audits by region to cut travel days between sites
- ✓Review which competence extensions would open the most subcontracted work
- ✓Keep a committed rate alongside the chargeable rate to catch overload
If you want to estimate what an increase is worth to you, try the savings calculator with your own auditor numbers.
Utilisation, travel and subcontracting move together
Utilisation rarely changes on its own. When a compliance and risk company raised utilisation from 74% to 85%, allocation time also fell by 99%. When a European certification body raised its internal share of work from 59% to 73%, days that had gone to subcontractors came back to its own team. The numbers are linked because they come from the same planning decisions.
Track them on one page each month. If utilisation rises while subcontracting stays flat, the extra work came from growth. If subcontracting falls and utilisation rises, the plan is using your people better.
Every subcontracted audit an internal auditor could have done is a utilisation point you already paid for.
For the full set of operations measures, read scheduling KPIs for inspection and certification bodies.
ScheduleAI is audit scheduling software built for testing, inspection and certification (TIC) organisations, with a planner approving every plan.
ScheduleAI plans the whole audit programme in one run, filling internal auditors first within competence, accreditation, rotation and travel rules, and reports utilisation per auditor. Planners review and approve every allocation.
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What is the formula for auditor utilisation rate?
Chargeable audit days delivered divided by available days, multiplied by 100. Available days are contracted days minus leave, public holidays, training and agreed non-audit duties.
Should travel time count towards utilisation?
Only if you invoice it as audit time. Most bodies exclude it from the chargeable rate and track it separately in a committed rate, so they can see overload.
Is 100% auditor utilisation a sensible target?
No. Auditors need time for travel, reporting, calibration, CPD and being observed. Aim for the highest rate your rules and people can sustain, and watch the committed rate.
How many working days should I assume per auditor?
Use your own HR data if you can. The savings calculator assumes 200 working days a year per auditor, or 1,650 working hours.
How does utilisation relate to subcontracting?
When internal auditors are under-used, work that they could do often goes to subcontractors. Read managing subcontracted auditors for how to track the two together.
Do technical experts count in utilisation?
Treat them separately. Their days are set by the audit team need, so mixing them into the auditor figure distorts it.