Bradford Factor

What is the Bradford Factor?

The Bradford Factor is a score for one employee’s absence over a set period, usually a rolling 52 weeks, calculated as S² × D: the number of separate spells of absence squared, multiplied by the total days absent. Because the number of spells is squared, frequent short absences score far higher than one long absence of the same length.

You will also see it called the Bradford score, Bradford formula or Bradford index. UK employers mostly use it for sickness absence, as a trigger in their absence policy: once a score passes a set point, the manager holds a review. Its name is usually traced to research at the Bradford University School of Management in the 1980s, although the university has never confirmed that the formula came from there.

Behind it sits the idea that short, unplanned absences cause more disruption than a single long one. A week off after an operation can be planned around. Six separate Mondays each leave a gap that someone has to fill at short notice.

How to calculate a Bradford score

Written out, the formula is B = S² × D. Work it out per employee in four steps:

1. Pick the period, usually the last 52 weeks counted back from today.

2. Count S, the number of separate spells of absence in that period.

3. Count D, the total number of days absent across all those spells.

4. Multiply S by itself, then by D.

A spell is one continuous absence, however long it lasts. Most policies count an absence that runs over a weekend or a rest day as one spell, so someone who is off on Friday and again on Monday has one spell of two working days. Write down how your policy counts it, because the score changes a lot either way.

For shift workers, D is the number of shifts or working days missed, not calendar days. A part-timer who works three shifts a week and misses one has one day of absence, the same as a full-timer who misses one of five. That keeps scores comparable across contracts, although a part-timer with the same number of spells will still reach a trigger with fewer days in total.

Worked example: two baristas, six days each

Two baristas in the same café were both off sick for six working days in the past year. Sam had one spell of six days after an operation: 1 × 1 × 6 = 6. Alex was off on six separate Mondays: 6 × 6 × 6 = 216. The days lost are identical, but Alex’s pattern left the Monday schedule short six times at short notice, and the score is 36 times higher.

Jo works three shifts a week and had three spells in the same year: one shift, two shifts and one shift. That is S = 3 and D = 4, so 3 × 3 × 4 = 36.

Common Bradford scores at a glance

These are scores that come up often, including the ones people search for most, such as 27, 36 and 64:

Three one-day absences in 12 months give a score of 27. Whether that is a problem depends entirely on the trigger points in your policy. Two scores can be the same for very different reasons: 64 can be four spells of one day each, or two spells adding up to 16 days.

What is a good or bad Bradford score?

No law sets a good or bad Bradford score. The employer decides the trigger points and writes them into the absence policy. A lower score is better, and a score of zero means no absence at all in the period. One set of trigger points that many UK policies use looks like this:

Treat these bands as an example. A busy restaurant that runs on a small team may set its first trigger lower, and a large site with a deep relief pool may set it higher. What matters is that the points are written down, applied to everyone in the same way, and that employees know them.

A Bradford score does not reset on a fixed date. With a rolling 52 weeks, each spell drops out of the calculation a year after it happened, so the score falls gradually as older absences leave the window.

The Bradford Factor and UK law

No law requires the Bradford Factor or defines it. Using it is lawful, but the score has to sit inside a fair absence process, and equality law limits what it may count.

Disability. Absence caused by a disability can make a high score something arising from that disability. Treating the employee unfavourably because of it is discrimination unless you can show it is a proportionate means of achieving a legitimate aim (Equality Act 2010, section 15). The duty to make reasonable adjustments (section 20) can mean leaving disability-related absence out of the score or setting a higher trigger for that employee.

Pregnancy. Treating a woman unfavourably because of illness she suffers as a result of her pregnancy, during the protected period, is pregnancy discrimination (section 18). Pregnancy-related sickness therefore stays out of the Bradford score.

A score is the reason to hold a conversation. A warning or a dismissal that rests on the number alone, without looking at the reasons behind the absences, is hard to defend at an employment tribunal.

Pros and cons for shift teams

In shift work the Bradford Factor measures something real. Every spell is a shift that has to be covered at short notice, often by someone on a day off, and a pattern of single days around weekends shows up quickly in the score. It is quick to calculate, the same rule applies to everyone, and it gives a manager a neutral reason to start a difficult conversation.

Its weaknesses are just as clear. The formula knows nothing about the reasons behind an absence, so a chronic condition such as asthma or epilepsy can push a score up without anyone doing anything wrong. It can also push people to come in while ill, which is presenteeism, and the union Unison has criticised it on exactly that point. Long-term absence barely registers. That is why many employers use the score next to the absence rate for the team, not on its own.

Using the Bradford Factor fairly

Settle the rules before anyone reaches a trigger, and put them in the absence policy:

• the period, usually a rolling 52 weeks

• what counts as one spell, including absences over rest days

• the trigger points and what happens at each one

• which absences are left out, at least those related to disability or pregnancy

• who calculates the score and how often

Then hold a short return-to-work conversation after every spell, before any score is involved. It is often where the real reason comes out: a childcare problem on Mondays, a shift pattern that does not work, or a health condition that needs an adjustment. When someone does reach a trigger, review those reasons first.

Finding the numbers in Shiftbase

When an employee calls in sick, the absence is recorded in Shiftbase against that employee, next to the schedule, and the empty shift can go straight out to the team. The Requests report then lists every absence per employee with start date, end date and number of days, filtered on absence type and period. Filter on sickness and the last 52 weeks, and you have S and D for each person on one screen. More on how sick calls and leave are handled in absence management in Shiftbase.