What this calculator does
The Bradford factor scores sickness absence by multiplying the number of separate spells, squared, by the total days taken. The squaring is the whole design: it deliberately treats eight one-day absences as far more disruptive than one eight-day absence, on the argument that unplanned gaps cost an employer more than a single predictable one.
The effect is dramatic. Eight days taken as one spell scores 8. The same eight days taken one day at a time scores 512, sixty-four times higher, for exactly the same amount of time away from work.
The formula
The score is S² × D, where S is the number of separate spells and D is the total days absent. Because S is squared, adding a spell matters far more than adding a day. Trigger points at which an employer begins a formal process are set by each organisation rather than by any standard, so the trigger here is a field rather than a built-in number.
| Term | Meaning |
|---|---|
| Spell | One continuous period of absence, however many days it runs. |
| Days absent | Total working days lost across all spells in the period. |
| Trigger point | The score at which an employer starts a review. Set locally, commonly somewhere between 50 and 500. |
| Rolling period | Usually twelve months. Scores from different window lengths are not comparable. |
The inputs explained
| Field | What to enter |
|---|---|
| Separate absence spells | Separate occasions of absence in the period, not days. Two days off in a row is one spell. |
| Total days absent | Total days absent across all those spells. Cannot be fewer than the number of spells. |
| Your first trigger point | Your organisation's first trigger point. There is no standard figure, so use the one in your own policy. |
When to use it
Seeing why the squaring matters
Hold the days at eight and change the spells. One spell scores 8, four spells score 128 and eight spells score 512. The time away is identical in all three; only the pattern changed.
Understanding a trigger
At four spells, a trigger of 50 is reached after just four days absent, because the spell count is already multiplying by sixteen. At one spell it would take fifty days. The same trigger means wildly different things depending on the pattern.
Checking a policy before applying it
Run the patterns your policy would actually catch. A trigger of 50 catches someone with four separate one-day absences spread across a year, which may or may not be what the policy intends.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much does the pattern matter?
The same total time away, split into a different number of spells.
| Separate spells | Bradford factor | Average days per spell | Against your trigger |
|---|---|---|---|
| 1 | 8 | 8.00 | 42 below the trigger |
| 2 | 32 | 4.00 | 18 below the trigger |
| 3 | 72 | 2.67 | at or over the trigger of 50 |
| 4 | 128 | 2.00 | at or over the trigger of 50 |
| 6 | 288 | 1.33 | at or over the trigger of 50 |
| 8 | 512 | 1.00 | at or over the trigger of 50 |
And how much do the days matter?
The pattern is fixed and the total time away grows.
| Days absent | Bradford factor | Against your trigger | Average days per spell |
|---|---|---|---|
| 3 | 27 | 23 below the trigger | 1.00 |
| 4 | 36 | 14 below the trigger | 1.33 |
| 8 | 72 | at or over the trigger of 50 | 2.67 |
| 12 | 108 | at or over the trigger of 50 | 4.00 |
| 20 | 180 | at or over the trigger of 50 | 6.67 |
Questions
Where does the squaring come from?
It is a design choice rather than a derivation. The metric was built on the view that unplanned short absences disrupt an employer more than one longer planned one, and squaring the spell count encodes that view strongly.
What trigger point should we use?
There is no standard. Organisations commonly set a first trigger somewhere between 50 and 200 with further points above it, and the right level depends entirely on the work and the workforce. That is why it is a field here.
Is the Bradford factor fair?
It is widely criticised, and the criticism is worth taking seriously. Because it punishes frequency rather than duration, it can score an employee with a chronic or fluctuating condition far above a colleague who took more total time off. Many employers exclude absence related to disability, pregnancy or a known long-term condition before scoring, and in some jurisdictions failing to do so creates legal risk.
Does it encourage the wrong behaviour?
It can. An employee near a trigger has an incentive to extend an existing absence rather than start a new one, because extra days are cheap and extra spells are not. That is the opposite of what most policies want.
Should a score alone trigger action?
No. It is a screening number that flags a pattern worth a conversation, not a finding about a person. Used as an automatic disciplinary threshold it will produce unjust outcomes, and most guidance says so.
For headline absence and churn figures see employee turnover rate, and for leave balances PTO accrual rate. Cover during absence is on staffing ratio.