How Absence Percentage Is Calculated
The absence rate formula is straightforward:
Absence rate (%) = (Days absent ÷ Total working days available) × 100
The total working days available should be the scheduled days for the period, excluding public holidays and pre-approved leave (annual leave, sick leave taken with prior approval, parental leave, and so on). What you are measuring is unplanned or unexpected absence against the working days that were available.
For example, if an employee was absent on 5 days during a year in which they were scheduled to work 200 days, their absence rate is (5 / 200) × 100 = 2.50%. The attendance rate is the inverse: 100 minus the absence rate, or (195 / 200) × 100 = 97.50%.
The Bradford Factor
The Bradford Factor is a scoring system designed to highlight the disruptive effect of frequent, short-term absence. The formula is:
Bradford Factor = S² × D
Where S is the number of separate absence episodes and D is the total number of days absent in the period.
The key insight is that S is squared, which means frequency has a disproportionately large effect on the score. Ten days off in a single episode gives a Bradford Factor of 1² × 10 = 10. Ten days off in five separate episodes gives 5² × 10 = 250, which is 25 times higher. This reflects the reality that one person being absent for two weeks is far less disruptive to a team than the same person calling in sick every other week throughout the year.
Bradford Factor Trigger Levels
| Bradford Factor Score | Typical Action |
|---|
| 0 to 49 | Within acceptable range. No formal action needed. |
| 50 to 199 | Informal conversation with manager may be appropriate. |
| 200 to 399 | Written warning or formal review often triggered. |
| 400 to 599 | Final written warning in many HR policies. |
| 600 or above | Grounds for formal disciplinary action in some policies. |
These thresholds vary between organisations. The Bradford Factor is a prompt for a conversation, not an automatic outcome. Many HR teams use it as one data point alongside pattern analysis (such as absences always on Mondays or Fridays), medical information, and individual circumstances.
What Is a Typical Absence Rate in New Zealand?
New Zealand employers generally report average unplanned absence rates of around 3 to 4 percent per year, or roughly 6 to 8 days per employee. The figure varies by sector: healthcare, retail, and manual trades tend to have higher rates than professional services and technology roles.
An absence rate below 2.5% is generally considered low. Rates of 5% or above may indicate systemic issues such as a poor working environment, excessive workload, lack of management support, or underlying health problems in the workforce. A high Bradford Factor alongside a moderate absence rate is often the most actionable signal, because it points to a pattern of repeated short absences rather than one-off events.
Worked Example
This matches the calculator's default inputs: 5 days absent, 1 episode, full year (52 weeks), five days per week = 260 total working days.
- Absence rate = (5 / 260) × 100 = 1.92%
- Attendance rate = 100 - 1.92 = 98.08%
- Bradford Factor = 1² × 5 = 5 (well within acceptable range)
If instead those same 5 days had been taken as 5 separate single-day absences, the Bradford Factor would be 5² × 5 = 125, moving into the informal conversation zone despite the same total absence. The absence rate would remain unchanged at 1.92%, illustrating that the Bradford Factor captures frequency while the absence rate only captures volume.
Related Calculators
Sources and method: Absence rate formula: (days absent / total working days) × 100, standard HR metric. Bradford Factor: S² × D, first published by Bradford University School of Management in the 1980s. Trigger levels are illustrative examples used widely in HR practice; thresholds vary by employer policy. NZ absence benchmarks: New Zealand Human Resources Institute (HRINZ) surveys and Statistics New Zealand labour market data.
This calculator provides indicative figures based on the inputs you enter. Absence management decisions should take into account individual circumstances, applicable employment law, and your organisation's HR policy. This is not legal or employment advice.
