Bradford Factor Calculator (absence spells² × days)

Understanding the Bradford factor calculator — concept and principle

This calculator works out the Bradford factor, a score that weights how often someone is absent more heavily than how long. It takes the number of separate absence spells and the total days absent, usually over a rolling 52 weeks, and shows the score, the average spell length and an example policy band. HR teams use it to flag patterns of frequent short absences for a supportive conversation.

Spells count twice — with the default inputs: B = 54.

How it is calculated

B = S × S × D

S = number of separate absence spells in the period
D = total days absent in those spells
Average days per spell = D ÷ S
The same days taken as one spell would score 1 × 1 × D = D

The example band follows one published local-government policy: below 20 no trigger, 20 to 50 informal stage, 51 or more formal stage.

The principle

Frequent short absences are often more disruptive than one long absence of the same total length, because each one is unplanned and hard to cover. Squaring the number of spells makes the score grow quickly with frequency. Ten days taken as one spell scores 1 × 1 × 10 = 10; the same ten days as five 2-day spells scores 5 × 5 × 10 = 250. The score is a trigger for attention, not a measure of how ill someone is.

Worked example

Defaults: 3 spells, 6 days in total.

B = 3 × 3 × 6 = 54.
Average days per spell = 6 ÷ 3 = 2.
The same 6 days as one spell would score 6.
54 is above 50, so the example band is 51 or more — formal stage in the example policy.

Each point is the calculator re-run with only “Total days absent in those spells” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Total days absent in those spells	Bradford factor score
1.5	13.5
3	27
4.5	40.5
6	54
7.5	67.5
9	81
12	108

How to read the result

Employers set their own trigger points, so the band here is only an illustration. A higher score means more frequent spells, not necessarily more days off. Two people with the same days absent can have very different scores. Use the score to start a conversation about causes and support, and check whether absences are linked to disability, pregnancy or a long-term condition, which need separate and fair handling under employment and equality law.

Common mistakes

Using a calendar year in one case and a rolling 52 weeks in another.
Counting one continuous absence that spans a weekend as two spells.
Applying triggers automatically without looking at the reasons.
Treating the example bands as a legal standard.

Keep in mind: The Bradford factor is a management tool, not a diagnosis or a judgement of conduct. Follow your organization's policy and local employment law.

Frequently asked questions

What is a high Bradford factor score?

It depends on the employer's policy. In the example policy used here, 51 or more leads to a formal meeting.

Why does the number of spells count twice?

Squaring it deliberately penalizes frequent short absences, which disrupt work more than one long absence.

Does a long-term sickness absence give a high score?

Usually not. One long spell gives S = 1, so the score equals the number of days.

Sources: Great Yarmouth Borough Council, Sickness Absence Management Policy, "Short-term absence"

Checked 9 Nov 2026. Bradford factor “O × O × D” (occurrences in a rolling 12 months squared × total days) and example trigger points (20–50 informal action; 51+ stage 1 meeting): Great Yarmouth Borough Council, Sickness Absence Management Policy, “Short-term absence”.

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