Calculate an employee’s Bradford Factor absence score from spells and days, or reverse it to find the days or spells needed to hit a trigger point.
Bradford Factor Formula
The Bradford Factor score is calculated by squaring the number of separate absence spells and multiplying by the total days absent:
B = S^2 * D
The calculator also solves the formula in reverse. To find the days of absence that would reach a target score at a fixed number of spells:
D = B / S^2
To find the number of spells that would reach a target score at a fixed number of days:
S = sqrt(B / D)
Variables:
- B is the Bradford Factor score
- S is the number of separate absence spells (occasions) in the rolling period, usually 52 weeks
- D is the total number of days absent across all of those spells in the same period
Because the spell count is squared, the formula gives far more weight to frequent short absences than to a single long one. Pick what you want to find at the top of the calculator. In score mode you enter spells and days and get the score plus which trigger band it falls in. In the two reverse modes you enter one known value and a target score, and the calculator returns the days or the spells that would reach it. The custom trigger option lets you replace the default trigger points with your own organisation’s thresholds.
How Absence Frequency Changes the Score
This is the part of the Bradford Factor that surprises people: the same total number of sick days can produce very different scores depending on how many separate times the person was off. The table below holds the total at 10 days absent and only changes how those days are split into spells.
| Spells (S) | Days (D) | Score (S² × D) | Typical reading |
|---|---|---|---|
| 1 | 10 | 10 | Below all triggers |
| 2 | 10 | 40 | Below first trigger |
| 3 | 10 | 90 | Above trigger 1 (51) |
| 5 | 10 | 250 | Above trigger 2 (201) |
| 10 | 10 | 1000 | Above trigger 4 (601) |
One person off sick for a single 10-day stretch scores 10. Another off for 10 single days scores 1000. That 100-fold gap is the whole point of the system, and it is why the score is used to flag frequent short absences rather than to judge total time lost.
The following illustrative trigger settings match the calculator defaults. They are not universal rules or recommended disciplinary thresholds; enter your organisation’s own policy settings.
| Score | Illustrative threshold |
|---|---|
| 51 | Trigger 1 |
| 201 | Trigger 2 |
| 401 | Trigger 3 |
| 601 | Trigger 4 |
Example Problems
Example 1: Score from spells and days.
An employee has been off on 4 separate occasions for a total of 8 days over the year. Square the spells and multiply by the days: B = 4 x 4 x 8 = 128. That is above the illustrative first trigger of 51 and below the second at 201. A score alone does not determine an employment outcome.
Example 2: Spells needed to reach a target.
You want to know how many separate absences it would take to reach a score of 200 if the total days off stays at 8. Use S = sqrt(200 / 8) = sqrt(25) = 5 spells. Five spells totalling 8 days score exactly 200, which remains below the illustrative trigger of 201. The same 8 days taken as one absence score 8.
Frequently Asked Questions
What counts as a spell of absence?
A spell is one continuous period away from work, no matter how many days it lasts. Three days off in a row for one illness is a single spell of three days. Being off Monday, then again the following Thursday, is two spells. The calculator needs the count of separate spells for S and the sum of all the days for D.
Is the Bradford Factor legal to use?
A score is not legal advice or an automatic disciplinary decision. Acas advises employers to consider individual circumstances and reasonable adjustments when using absence review points; pregnancy-related sickness should not count towards review points. Follow the applicable policy and employment law.
What is a high Bradford Factor score?
There is no universal cutoff. The calculator’s example thresholds are editable; use the organisation’s policy. Because the spell count is squared, frequent absences increase the score, but the score does not explain their cause or determine an appropriate response.
