What Is the Bradford Factor? Formula & Examples
The Bradford Factor scores absence by disruption, not just total days. Learn the formula (S² × D), worked examples, trigger bands, and where it falls short.
Two employees each took 10 days off this year. One took a single two-week holiday. The other was off for 10 separate single days, scattered with no notice. On a spreadsheet they look identical — both "10 days." In reality, the second pattern is far more disruptive to a team.
The Bradford Factor is a simple formula that captures exactly this difference. Here's how it works, worked examples, and — just as importantly — where it goes wrong.
What is the Bradford Factor?
The Bradford Factor is an absence-scoring method that weights frequent, short, unplanned absences much more heavily than occasional long ones. The thinking: a person off sporadically and without notice is harder to plan around than someone who takes one planned block.
It produces a single number per employee, which makes it easy to spot patterns — and easy to misuse, so read to the end.
The Bradford Factor formula
B = S² × D
Where:
- S = the number of separate spells (instances) of absence in a set period (usually a rolling 12 months)
- D = the total number of days absent across those spells
The key is that S is squared. The number of separate occasions drives the score far more than the total days. That's the whole point — frequency is penalised more than duration.
Worked examples
Watch what happens to three people who were all absent for the same total of 10 days:
| Employee | Spells (S) | Total days (D) | Calculation | Bradford score |
|---|---|---|---|---|
| Alex | 1 spell of 10 days | 10 | 1² × 10 | 10 |
| Sam | 3 spells (4 + 4 + 2) | 10 | 3² × 10 | 90 |
| Jordan | 10 spells of 1 day | 10 | 10² × 10 | 1,000 |
Same ten days. Scores of 10, 90, and 1,000. The maths makes the pattern visible in a way a day count never can.
Common trigger bands
Many organisations set "trigger points" where a score prompts a conversation. These numbers are set by each company, not fixed by law — treat the following only as a common illustration:
- 51 — an informal chat / check-in
- 201 — a formal review
- 401 — a more serious process
The right thresholds depend entirely on your industry, role types, and culture. A frontline shift operation and a salaried remote team should not use the same numbers.
How to use it fairly (this part matters)
The Bradford Factor is a flag, not a verdict. Used carelessly it punishes people for things they can't control. Before acting on any score:
- Exclude what should be excluded. Pregnancy-related absence, disability-related absence, and pre-planned leave should not inflate someone's score. In many places, penalising disability- or pregnancy-related absence can be unlawful discrimination — take advice.
- Look at context, not just the number. A high score can mean a genuine health issue, caring responsibilities, or burnout — not "unreliability."
- Be transparent. Tell staff how it's calculated and what the thresholds are. A secret score used against people destroys trust.
- Treat it as the start of a conversation, never an automatic penalty.
Criticisms and limits
It's worth being honest about the downsides:
- It can discourage people from taking legitimate sick days, pushing presenteeism (working while ill), which often makes things worse.
- It treats all short absences the same, regardless of cause.
- A single bad patch (say, a string of migraines one quarter) can produce an alarming number that misrepresents someone.
Used as one input among many — alongside a real conversation — it's useful. Used as an automatic disciplinary trigger, it's a liability.
How to calculate it automatically
You can compute the Bradford Factor by hand, but with a rolling 12-month window per employee it becomes tedious and error-prone fast — exactly the kind of thing software should do for you.
Absenca calculates Bradford Factor scores automatically from real leave and sickness data, with risk levels, so you can spot genuine patterns without maintaining a spreadsheet of spells and days. Because it's reading the same data your team already logs for time-off tracking, there's nothing extra to maintain.
Frequently asked questions
What's a "good" Bradford Factor score? Lower is better, and many teams consider anything under ~50 unremarkable. But there's no universal "good" number — it depends on the thresholds your organisation sets and the nature of the work.
What time period does it cover? Most organisations use a rolling 12-month window, so the score reflects recent patterns rather than someone's entire history.
Does long-term sickness produce a high score? No — and that's by design. One long spell has S = 1, so the score stays low (the formula targets frequent short absences, not serious illness).
Is using the Bradford Factor legal? The method itself is legal, but how you apply it can cross into discrimination if it penalises protected absences (e.g. disability or pregnancy related). Always take local employment-law advice before tying it to any formal process.