How this instrument works
The Bradford Factor turns two counts — how many separate spells of absence someone had, and how many days those spells added up to — into a single score that penalizes fragmentation on purpose. Squaring the spell count before multiplying by the day total means five one-day absences produce a score twenty-five times higher than a single five-day absence carrying the same total days away from work, because scattered short absences are harder for a manager to plan around than one predictable stretch.
The formula is usually attributed to research done at the Bradford University School of Management in the 1980s, though the university itself has never confirmed the connection and the original study has never surfaced — the name stuck regardless, and UK employers adopted the score widely enough that HR software still ships it as a built-in field. It sits inside an absence policy as a scored trigger: cross a set number of points in a rolling window and the file gets flagged for a review meeting, not an automatic warning.
The score cannot tell a documented illness apart from a pattern of unplanned Monday absences — both produce the same spell count and day total, and both square the same way. It also carries no built-in adjustment for absence linked to disability, pregnancy or a single long medical leave, which is why UK guidance treats a high score as the start of a conversation rather than a verdict, and why several unions have argued the formula should never sit inside a disciplinary process unmodified.
- Enter Number of separate absence spells — count each distinct period away from work once, however many days it ran.
- Enter Total days absent — the sum of every day missed across all of those spells in the period you are reviewing.
- Read Bradford Factor — the instrument squares the spells and multiplies by the days automatically.
- Compare the score against your own policy's trigger points, since no outside body sets a universal threshold.
- Recalculate on a rolling period, commonly the trailing 52 weeks, rather than a fixed calendar year, to match how most absence policies define the window.
Worked example — four spells, ten days
Take an employee whose file shows four separate spells of absence this year — a single sick day in February, two days out with flu in April, a one-day absence in July, and a four-day stretch in October — totaling ten days away from work. Enter 4 as Number of separate absence spells and 10 as Total days absent, and the instrument squares 4 to get 16, then multiplies by 10 for a Bradford Factor of 160.
A colleague who took the same ten days off in one block, recovering from a scheduled procedure, scores only 10 — sixteen times lower, even though the total days missed match exactly. That gap is the entire point of the formula: two employees who cost the schedule the same number of missed workdays can carry very different scores, because it is the four separate returns and re-plannings, not the ten days themselves, that the Bradford Factor is built to weigh.
Questions
What counts as one absence spell?
Any continuous period away from work counts as a single spell, no matter how many days it runs — a five-day flu absence is one spell, not five. A new spell starts only when the person returns to work and then goes absent again, so counting spells wrong, such as splitting one illness across two rows, understates the fragmentation the formula exists to catch.
Why does the formula square the number of spells instead of just adding them?
Squaring makes the score grow much faster with frequency than with duration, on purpose. Doubling the spell count while holding days fixed roughly quadruples the score, while doubling the days with spells fixed only doubles it — the formula is built to flag someone with many short absences well before someone with one long, documented absence reaches the same number.
What Bradford Factor score should trigger a review?
There is no statutory number. Acas guidance describes trigger points as a policy choice, not a legal requirement, though a commonly cited scheme reviews at 50 points, escalates at 100, and treats 400-plus as a formal concern, measured over a rolling 12-month window. Acas is explicit that reaching a trigger should open a supportive conversation, not launch an automatic disciplinary step.
Can a high score be used to discipline an employee with a disability?
Not without adjustment. Under the Equality Act 2010, absence linked to a disability can require reasonable adjustments to how trigger points apply — Acas guidance gives excluding disability-related absence from the count, or raising the threshold, as examples. Running the raw score through a standard trigger point without that adjustment risks treating protected absence the same as an unrelated attendance pattern.
How is this different from an absence percentage or attrition rate?
Absence percentage divides missed days by scheduled days and treats every absence the same regardless of how it was spread out; attrition rate measures people leaving the organization entirely, not time missed by people who stay. The Bradford Factor is the only one of the three that reacts to pattern — it distinguishes one long absence from several short ones covering the identical number of days.
Over what period should spells and days be counted?
Most policies use a rolling period, commonly the trailing 52 weeks from today rather than a fixed calendar year, so a spell from eleven months ago still counts but one from thirteen months ago has aged out. Recalculating on a fixed date instead of a rolling window will understate or overstate the score depending on when absences happened to cluster.
References
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.