Average Working Hours Per Week: An Employer Guide!

This article is about how average weekly working hours work in UK law, and what HR and business leaders need to have in place to stay compliant while still running a productive operation. It explains the 48-hour weekly limit, how averages are calculated in practice, when opt-outs are legitimate and how employers should monitor and manage working time risk.

Average working hours sit at the junction of employment law and health and safety. The Working Time Regulations 1998 (WTR) limit most workers to an average of 48 hours per week, calculated over a set “reference period”. In reality, many organisations rely on overtime, irregular shifts and flexible patterns that make the numbers far less straightforward than the headline rule suggests. For HR, the risk is that hours creep up without proper monitoring, with potential consequences for wellbeing, performance and regulatory exposure.

From an employer’s perspective, the legal test is not the busiest week but the underlying pattern over time. You need to know which hours count, how to treat travel, on-call and training time, how to handle part-timers and workers with several jobs, and when you can rely on a valid opt-out agreement. You also need to be able to evidence your approach if challenged by an inspector, trade union or claimant.

What this article is about
This article gives HR directors and business owners a structured guide to average weekly working hours under UK law. It covers the legal definition and reference periods, how to calculate the average for different working patterns, when and how workers can opt out of the 48-hour limit, and the practical steps HR should take to monitor hours and manage risk. The aim is to give you a clear framework you can apply across your workforce, rather than leaving managers to make ad hoc judgments.

Section A: Legal Definition of Average Working Hours

Average working hours have a specific legal meaning under the Working Time Regulations 1998. This section explains what counts as working time, what does not, and how the 48-hour limit is assessed for compliance purposes. Employers need a precise understanding of these definitions because they inform contractual drafting, monitoring duties and health and safety risk management.

The statutory framework is built around the principle that workers should not, over time, be required to work more than an average of 48 hours per week unless they have validly opted out or fall within a specific statutory exemption. Regulation 4 WTR sets the maximum average weekly working time. The law looks at the pattern of work across the reference period rather than any individual busy week.

1. Statutory basis: Working Time Regulations 1998

The 48-hour limit is set out in the WTR. Regulation 4 establishes the maximum average weekly working time unless the worker signs an individual opt-out under regulation 5, or falls within an excluded sector or special case where the rule does not apply. Employers must take “all reasonable steps” to ensure the 48-hour limit is not exceeded.

2. What hours count toward the average

Working time is defined as any period during which the worker is working, at the employer’s disposal and carrying out their activities or duties. This generally includes:

• Normal working hours
• Overtime (paid or unpaid) actually worked
• Mandatory training
• Travel between work assignments
• On-call time at the workplace or when the worker is significantly restricted

3. What hours do not count

These periods normally do not count as working time:

• Rest breaks and rest periods
• Home-to-work travel
• On-call periods where the worker is free to use their time as they wish
• Genuinely occasional voluntary overtime
• Unpaid breaks where the worker is relieved of duties

4. The 48-hour limit and the reference period

The 48-hour cap is averaged over a reference period. For most adult workers this is 17 consecutive weeks. In specific sectors or via a collective or workforce agreement, the reference period can be extended to 26 weeks or up to 52 weeks (for example, offshore work). Short-term peaks above 48 hours do not breach the law provided the average over the reference period remains within the limit.

5. Record-keeping and evidential burden

Employers must keep adequate records to show compliance with the 48-hour limit, night work limits and opt-outs, retaining these for at least two years. Although post-Brexit reforms allow more flexibility in how time is recorded, employers must still be able to evidence compliance. If hours are not recorded adequately, it becomes difficult to demonstrate that limits have not been breached.

Section A Summary
Employers need clarity on what counts as working time, how the 48-hour average is calculated and what records must be maintained. Failure to apply these definitions correctly leads to miscalculations, inconsistent scheduling and an inability to evidence compliance.

Section B: Calculating the Average Weekly Limit

Calculating average weekly working hours requires applying the correct reference period, categorising working time accurately and using consistent methods across the business. This is particularly important in organisations with irregular hours, shift work or overtime.

The calculation is based on the statutory reference period rather than single-week totals. This gives employers flexibility, but it also requires accurate hour-by-hour data.

1. Standard reference period (17 weeks)

For most workers, the reference period is 17 consecutive weeks. The average is calculated by dividing total hours worked in the period by 17. If the worker has been employed for less than 17 weeks, the period of actual employment is used.

2. When the 26- or 52-week reference periods apply

A 26-week reference period may apply to “special case” workers such as those involved in continuity of service or production. A 52-week reference period is used for certain offshore roles and may also be established by collective or workforce agreement. Employers must document and justify any extended reference period.

3. Irregular hours, shift work and compressed hours

Key points:

• Shift workers: include all rostered hours and required handover time
• Variable or zero-hours roles: include hours actually worked
• Compressed hours: long days do not cause a breach if the average remains compliant
• Seasonal workers: ensure the reference period used reflects peaks and troughs

4. Paid and unpaid breaks

Breaks must be treated correctly:

• Paid breaks count as working time
• Unpaid breaks do not count
• Interrupted breaks count for the interrupted portion

5. Practical calculation examples for employers

Example 1: Standard worker over 17 weeks
Total hours worked: 780
Average = 780 ÷ 17 = 45.88 hours
This is compliant.

Example 2: Worker with peak periods
Weeks 1–4: 60 hours per week
Weeks 5–17: 40 hours per week
Total = (4 × 60) + (13 × 40) = 240 + 520 = 760
Average = 760 ÷ 17 = 44.7 hours
Still compliant, despite several 60-hour weeks.

Example 3: Shift worker with compressed hours
12-hour shifts, 4 days per week = 48 hours
Average = 48 hours
Compliant unless additional overtime pushes the average above 48.

Section B Summary
Employers must use the correct reference period and treat working time consistently. HR systems must record actual hours worked, including overtime and interrupted breaks. Incorrect categorisation or inconsistent record-keeping can distort averages and undermine compliance.

Section C: Opt-Outs from the 48-Hour Limit

Workers may choose to opt out of the 48-hour limit, but only if strict legal requirements are met. Opt-outs create flexibility but do not remove the employer’s duty to monitor working time and manage fatigue.

Opt-outs provide operational scope in sectors with fluctuating demand, but employers must still ensure workers are not pressured into signing, that withdrawals are respected and that working time is continuously monitored even after an opt-out is in place.

1. Validity requirements for individual opt-outs

An opt-out must:

• Be in writing
• Be voluntary
• Be signed by the worker
• Clearly state agreement to disapply the 48-hour limit

Opt-outs may be included in employment contracts, but workers must be told clearly that signing is optional and refusal will not result in detriment.

2. Voluntariness, withdrawal rights and notice periods

Workers cannot suffer any detriment for refusing to sign or for withdrawing an opt-out. Withdrawal does not require a reason. The default notice period is seven days unless a longer period, up to a maximum of three months, is agreed in writing.

3. Restrictions for young workers

Workers aged 16–17 cannot sign an opt-out. They are subject to stricter limits:

• Maximum 8 hours per day
• Maximum 40 hours per week
• No averaging and no opt-out permitted

4. Sector-specific exemptions and special cases

The 48-hour limit does not apply in certain sectors or roles, including:

• Air, rail, road, sea and inland waterway transport
• Sea fishing and other work at sea
• Certain armed forces, police and civil protection activities
• Genuine unmeasured working time roles where the worker determines their own hours

Some roles with continuity-of-service requirements have different rules on rest or reference periods, but the 48-hour limit usually still applies unless expressly disapplied.

5. Employer duties when opt-outs are in place

Employers must:

• Continue monitoring working hours
• Assess and manage fatigue risk
• Provide statutory daily and weekly rest
• Review opt-outs regularly
• Retain opt-out records for at least two years

A signed opt-out does not allow employers to ignore working time obligations or health and safety risk.

Section C Summary
Opt-outs must be voluntary, written and clearly explained. They do not remove the employer’s responsibility to monitor hours, manage fatigue or ensure rest. Compliance issues usually arise where opt-outs are treated as a blanket exemption without ongoing monitoring.

Section D: Compliance, Monitoring and HR Risk Management

Working time compliance is part of wider health and safety duties. HR must ensure systems, record-keeping and workplace practices all support compliance. The Working Time Regulations give employers flexibility through reference periods and opt-outs, but they also impose strict duties to monitor hours, prevent fatigue and maintain accurate records.

Many compliance failures arise from inconsistent monitoring, unclear expectations or managers bypassing formal processes to meet operational pressure. A structured compliance framework protects both the employer and the workforce.

1. Required employer controls and monitoring duties

Employers must maintain adequate records to evidence compliance with:

• The 48-hour weekly limit
• Night work limits
• Young worker requirements

Records should distinguish paid and unpaid breaks and reflect actual hours worked, including overtime and interrupted breaks. Digital systems are strongly recommended, especially for shift-based or multi-site operations.

2. Health and safety implications

Excessive hours increase health and safety risks. Employers must consider:

• Fatigue and error risk in safety-critical roles
• Driving roles governed by sector-specific rules
• Mental health impacts of prolonged overwork
• Workload fairness, team capacity and turnover

Working time should be considered explicitly in risk assessments, particularly where overtime or variable hours are common.

3. Managing overwork complaints

Working time complaints should be treated as potential compliance issues. Appropriate steps include:

• Reviewing time records over the full reference period
• Adjusting schedules or reallocating work
• Reinforcing limits with managers
• Ensuring no detriment to workers who raise concerns
• Recognising when complaints may constitute whistleblowing

Failure to address such concerns may escalate into grievances or claims of detriment or constructive dismissal.

4. Enforcement risk and penalties

The HSE and local authorities enforce working time rules. Potential consequences include:

• Improvement notices requiring operational changes
• Prohibition notices in serious cases
• Criminal prosecution for deliberate or significant breaches
• Civil claims involving detriment or dismissal
• Reputational damage, particularly in public-facing sectors

Most enforcement action stems from inadequate monitoring and weak record-keeping rather than intentional non-compliance.

5. Best practice: contracts, policies and audit processes

A robust compliance framework should include:

• Clear contractual definitions of working time, overtime and opt-out arrangements
• A Working Time Policy setting expectations for managers and staff
• Routine audits comparing recorded hours with schedules
• Annual reviews of opt-outs, considering necessity and safety
• Manager training on working time obligations
• Integration of WTR rules into HRIS, rostering and payroll systems

Embedding these controls ensures managers cannot unintentionally sidestep legal obligations when operational pressure increases.

Section D Summary
Compliance depends on accurate data, consistent monitoring and proactive management of fatigue and overwork. Strong HR controls transform working time compliance from a reactive burden into a manageable part of operational governance.

FAQs

1. What is the maximum number of hours someone can work in a week?

Most adult workers must not work more than an average of 48 hours per week, calculated over the relevant reference period (usually 17 weeks). Individual weeks may exceed 48 hours provided the overall average remains compliant and rest requirements are met. Some sectors and autonomous roles are excluded, but these exemptions are narrowly defined.

2. Can an employer force staff to sign an opt-out?

No. Opt-outs must be voluntary. Workers cannot be dismissed, disciplined or treated detrimentally for refusing to sign or for later withdrawing an opt-out. Even where opt-out clauses appear in standard contracts, employers must make clear that signing is optional.

3. Do travel time, training and on-call hours count?

Travel between work assignments, mandatory training and on-call time spent at the workplace usually count as working time. Home-to-work travel and on-call periods where the worker is free to use their time as they wish normally do not. The classification depends on whether the worker is working, at the employer’s disposal and carrying out duties.

4. Can the working hours average exceed 48 hours temporarily?

Yes. Short-term peaks above 48 hours are permissible provided the average across the full reference period remains within the limit. If a sustained pattern pushes the average above 48 hours, an opt-out or organisational adjustment will be required unless the role is genuinely exempt.

5. How should employers handle employees with multiple jobs?

Employers must take all reasonable steps to ensure the combined hours from all jobs do not exceed the 48-hour average limit. This may involve requesting information about hours worked elsewhere, documenting reasonable enquiries and adjusting work patterns if necessary. Employers do not typically need to verify third-party records but must show sensible steps have been taken.

Conclusion

Average weekly working hours are a core compliance obligation under the Working Time Regulations, and they require structured oversight from HR rather than informal management. The 48-hour limit, the rules on what counts as working time and the use of reference periods give employers flexibility, but they also impose clear duties to monitor hours accurately, manage fatigue risk and maintain lawful opt-out processes.

A compliant employer will have reliable time recording, clear documentation, consistent calculations and a proactive approach to resolving overwork concerns. By embedding these controls into contracts, policies and rostering systems, HR directors can protect the organisation from enforcement action, strengthen workforce wellbeing and ensure that working time risk is managed with the same discipline as any other regulatory requirement.

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