Definition · HR operations and employee relations
Bradford Factor
Definition
Bradford Factor is an absence score that weights how often someone is absent more heavily than how long. It is calculated as the number of separate absence spells squared, multiplied by the total days absent, over a rolling period, usually 52 weeks. Frequent short absences produce much higher scores than one long absence.
Also called: Bradford formula, Bradford factor score, Bradford index
Formula
Bradford Factor score = S × S × D
- S
- Number of separate spells (instances) of unplanned absence in the period. Three single sick days on different dates count as three spells; a five-day illness counts as one.
- D
- Total number of days (or shifts) of unplanned absence in the same period.
- Period
- Usually a rolling 52 weeks, so old absences drop off over time.
Worked example
Maria has one 10-day absence in a year: 1 × 1 × 10 = 10. James has ten separate one-day absences: 10 × 10 × 10 = 1,000. Priya has five spells totaling 8 days: 5 × 5 × 8 = 200. All three missed a similar amount of time, but James's score is 100 times Maria's.
Why the Bradford Factor weights frequency
The idea, associated with research at the Bradford University School of Management in the 1980s, is that short, frequent, unplanned absences disrupt work more than a single long one. A planned two-week absence for surgery can be covered with a temp or overtime arranged ahead of time. Ten unannounced Mondays mean ten mornings of scrambling, missed service levels and coworkers picking up the slack.
Squaring the number of spells is what creates that effect. Doubling spells quadruples the score, while doubling days only doubles it. That is why the measure is popular in contact centers, warehouses and manufacturing, where every unexpected gap on a shift has a cost that day.
How to calculate it in practice
Use a rolling 52-week window recalculated each time a new absence is recorded. Decide in writing what counts as a spell: most employers count consecutive working days of absence as one spell even across a weekend, and treat a partial shift (leaving early sick) as a spell of a half day or one day.
What to exclude matters more than the arithmetic. Approved vacation, holidays, jury duty, bereavement and any legally protected absence should be left out. In the US that includes FMLA leave, leave given as an ADA accommodation, and time covered by state or local paid sick leave laws, many of which bar counting protected sick time against an employee. Our page on absenteeism covers the broader measures that sit alongside a Bradford score.
A Bradford Factor calculator is simple to build in a spreadsheet: one row per absence spell with start date and days, a filter for the last 365 days, then COUNT of spells squared times SUM of days. Most time and attendance or HRIS systems can calculate it automatically.
Typical trigger points
There is no official scale. Employers set their own trigger points, and a common pattern looks like this:
- Around 50: informal conversation with the manager.
- Around 125 to 200: formal attendance review meeting, possibly a verbal or first written warning.
- Around 400 to 500: final written warning.
- Around 650 or more: consideration of dismissal.
These should be prompts for a conversation, not automatic outcomes. A score of 250 driven by a newly diagnosed condition needs a very different response from a score of 250 driven by a pattern of Friday absences.
Bradford Factor vs attendance points
In the US, hourly employers more often use an attendance point system, which assigns points per occurrence (for example 1 point for an absence, half a point for a tardy) and rolls points off after 12 months. Points are easier for employees to understand and track themselves. The Bradford Factor is more common in the UK and Commonwealth countries and suits organizations that mainly want to flag frequent short absences rather than lateness. Some employers use both: points for discipline, Bradford for reporting. If you go the points route, our attendance points policy template is a ready-made starting point.
Legal risks and fair use
The biggest risk is counting absences that the law protects. In the UK, disability-related absence needs careful handling under the Equality Act 2010, and employers are generally expected to consider reasonable adjustments, which may include higher trigger points. Pregnancy-related absence must not count. In the US, the regulations under the FMLA prohibit counting FMLA-protected leave under no-fault attendance policies, the ADA can require flexibility as a reasonable accommodation, and the Pregnant Workers Fairness Act adds accommodation duties for pregnancy-related limitations. Rules vary by state and country.
Good practice: publish the method and trigger points in your attendance policy, review every case before acting, record the reasons for any exception, and look at scores by team and demographic group to check the system is not falling harder on one group.
Frequently asked questions
What is a good Bradford Factor score?
Lower is better. A score under about 50 rarely raises concern in most organizations. Anything over 100 to 200 usually triggers a review. There is no universal standard, so the meaningful comparison is against your own trigger points and team averages.
How do you calculate a Bradford factor score?
Count the separate absence spells in the last 52 weeks (S) and the total days absent (D). Multiply S by itself, then by D. Five spells and seven days gives 5 × 5 × 7 = 175.
Is the Bradford Factor legal in the US?
Using it is legal, but you must exclude protected absences such as FMLA leave, ADA-related absences and leave protected by state paid sick leave laws, and apply it consistently. Have counsel review the policy, particularly if you operate in several states.
Does the Bradford Factor include lateness?
Usually not. It was designed for absence spells. Employers that want to manage lateness tend to track it separately or use an attendance point system that gives partial points for tardies and early departures.
Is the Bradford Factor fair?
It is consistent and simple, but it can penalize people with recurring health conditions or caring duties. Treat scores as a trigger for a conversation, exclude protected absences and allow adjustments where they are needed.