The Bradford factor: formula, examples and limits
Ten days of absence can mean two very different things: one person recovering from surgery, or another disappearing for a day or two every other week. The Bradford factor is a simple score that tells these two situations apart - and it is worth understanding both its arithmetic and its blind spots.
The formula
The score multiplies the number of separate spells of absence by itself, then by the total days:
B = S × S × D
- S - the number of separate absence spells over a period (usually the last 52 weeks);
- D - the total number of days absent over the same period.
Because S is squared, frequency dominates duration. The same ten days produce wildly different scores:
| Pattern | Spells (S) | Days (D) | Score |
|---|---|---|---|
| One spell of 10 days | 1 | 10 | 10 |
| Two spells of 5 days | 2 | 10 | 40 |
| Five spells of 2 days | 5 | 10 | 250 |
| Ten spells of 1 day | 10 | 10 | 1000 |
That is the whole idea: ten Mondays hurt the team more than one two-week spell, because every short absence breaks plans, shifts meetings and reshuffles other people’s work.
Thresholds people actually use
There is no official scale - the thresholds are conventions that companies adapt to their own reality. A common starting point: up to 50 is background noise; around 125 is worth a caring conversation; 250 and above deserves attention as a pattern. Treat these as tripwires for a conversation, not as verdicts.
Where the metric stops working
The Bradford factor counts patterns, not reasons. It cannot tell a fading commitment from a chronic illness, a difficult pregnancy or a parent with a sick child - and applied blindly, it punishes exactly the people who need support. In several countries, mechanical sanctions triggered by a score would also collide with employment and disability law.
Counting it without a spreadsheet
The arithmetic is trivial; the bookkeeping is not. To keep the score honest you need every absence recorded as a spell with dates, a rolling 52-week window, and the discipline to never miss a one-day sick leave - the exact kind of record-keeping that erodes in a spreadsheet by March.