The four-day work week is no longer a fringe idea. Following successful national trials in Iceland, the UK, Germany, and Australia, and high-profile adoptions by companies ranging from Microsoft Japan to Kickstarter, the question for most US HR teams is no longer whether it is possible — it is how to implement it responsibly. This guide provides a structured roadmap for HR leaders who need to evaluate, pilot, and potentially roll out a four-day work week without compromising operational performance or creating legal exposure.

Understanding the Two Models

Before anything else, HR leaders must clarify which model they are evaluating, because the implications differ significantly:

100-80-100 vs. 4x10: two very different things

The 100-80-100 model: 100% of pay, 80% of the time (32 hours over 4 days), with the expectation of 100% output. This is the model studied in the major national trials and the one most associated with genuine wellbeing and productivity benefits. The 4x10 compressed schedule: 40 hours over four 10-hour days, with the same total hours. This improves scheduling flexibility but does not reduce total work time and shows weaker wellbeing outcomes in research.

This guide focuses primarily on the 100-80-100 model, as it is the version supported by the strongest evidence and the most significant HR challenge.

Phase 1: Feasibility Assessment (Weeks 1-4)

Not every business is equally suited to a four-day work week. The feasibility assessment determines whether a pilot is viable and which parts of the organization are best positioned to run it first.

Business Model Analysis

Assess each business function against four criteria:

  • Output measurability. Can you objectively measure whether work is getting done at the same level in 32 hours? Knowledge work with clear deliverables is more amenable than process work measured by time.
  • Coverage requirements. Does the role require five-day coverage for customers or partners? If so, a rotation or staffing model may be needed rather than a blanket four-day schedule.
  • Interdependence. How tightly coupled is this team's work to other teams or external parties who operate on a five-day schedule?
  • Process efficiency opportunity. Switching to 32 hours requires eliminating or redesigning the work that fills the fifth day. Teams with meeting-heavy, low-output Fridays have more room to absorb the reduction than teams with uniformly high output demands.

Before any pilot, review these legal considerations with employment counsel:

  • FLSA overtime for non-exempt employees. Under federal law, overtime is triggered at 40 hours per week. A 32-hour week eliminates overtime risk for non-exempt employees. However, verify that you are not inadvertently reducing pay for non-exempt employees — their hourly rate must remain the same, so a 32-hour week at the same weekly pay effectively increases their hourly rate.
  • State daily overtime laws. California, Nevada, Alaska, and a handful of other states impose daily overtime for hours worked beyond 8 in a single day. If you are considering 4x9 or 4x10 compressed models, this is a live issue.
  • Employment contracts. Review whether any existing employment agreements specify a five-day work week or 40-hour work week that would require contract amendments or employee consent before changes.
  • Benefits implications. Benefits tied to full-time status (typically defined as 30+ hours per week for ACA purposes) are generally unaffected by a 32-hour week. However, review any benefits that calculate based on hours worked.

Phase 2: Pilot Design (Weeks 5-8)

A well-designed pilot generates usable data. A poorly designed pilot generates noise that management cannot act on.

Pilot Scope

Select a pilot group that is:

  • Large enough to generate statistically meaningful data (at minimum 15 to 20 people)
  • Representative of roles where the four-day model is most viable
  • Distinct enough from non-pilot teams that contamination effects are manageable
  • Led by a manager who is genuinely supportive of the pilot, not reluctantly compliant

Pilot measurement framework

Before the pilot begins, establish baselines for: output metrics (deliverables completed per week, project milestone completion rate), quality metrics (error rates, customer satisfaction scores, rework rates), wellbeing metrics (pulse survey scores on stress, energy, and work-life balance), and retention signals (voluntary turnover intent survey). Measure all of these at 30, 60, 90, and 180 days.

Operational Redesign

The most important, and most skipped, part of four-day week implementation is redesigning how work gets done. The fifth day does not disappear — the work that filled it must be eliminated, automated, or redistributed. Facilitate workshops with pilot teams to:

  • Map all recurring meetings and eliminate those without clear outcomes
  • Identify administrative tasks that can be automated or batched
  • Establish async communication norms that reduce synchronous meeting time
  • Set clear output expectations so employees know what success looks like in 32 hours

Phase 3: Pilot Execution (Months 2-7)

Run the pilot for a minimum of six months. Collect data monthly. Hold brief retrospectives with the pilot team every four weeks to surface operational problems early and make adjustments before they become entrenched.

Common issues to monitor:

  • Meeting migration. Meetings that previously happened on Friday may simply compress into the remaining four days, increasing meeting density without reducing total meeting time.
  • Burnout risk. Some employees try to maintain five-day output in four days by working longer hours on the four working days. Track actual hours worked, not just stated schedule.
  • Coverage gaps. Monitor whether customer-facing metrics (response time, SLA compliance) change during the pilot.
  • Equity concerns. Teams not in the pilot may feel resentment. Communicate transparently about the pilot's purpose and timeline for potential broader rollout.

Phase 4: Decision and Rollout

At pilot completion, evaluate the data against your pre-defined success criteria. A successful pilot typically shows:

  • Output metrics maintained at 95%+ of baseline
  • Employee wellbeing scores improved
  • No degradation in quality metrics
  • Turnover intent scores improved

If the pilot succeeds, create a rollout plan that sequences expansion by business function, with operational redesign workshops preceding each team's transition. Not every team will be appropriate for the model — some will require hybrid solutions or remain on standard schedules with transparent rationale.

Implementing a four-day work week raises employment law questions that many organisations overlook until implementation is underway. The specifics depend on whether you are adopting the 100-80-100 model (reduced hours, maintained pay) or the compressed 4x10 model (same hours, different schedule) — and on the jurisdictions in which you operate.

For the 100-80-100 model (32 hours):

In the US, reducing weekly hours for non-exempt employees changes how overtime is calculated under FLSA. If the standard working week is now 32 hours, hours beyond 32 but below 40 are not federal overtime. Some employers explicitly define the new standard in updated employment agreements to avoid ambiguity. Note that several states (California, Colorado, Nevada) have daily overtime rules that trigger at 8 hours per day — applicable even on a four-day schedule if shifts run longer than 8 hours.

In the UK, reducing contracted hours requires a contract variation. The employer and employee must agree to the new terms in writing. For employees on collective agreements, union consultation may be required before hours can be changed. Salary is typically maintained at the current level (which is the whole point of the 100-80-100 model), so this is a favourable variation in terms of pay, but the formal process still applies.

Part-time workers and pro-rata rights: UK law provides that part-time workers must not be treated less favourably than comparable full-time workers. If some employees shift to 32 hours while others remain at 40 hours, ensure that benefits, training access, and promotion opportunities are applied proportionately and that no protected groups are disproportionately excluded from or included in the four-day week.

For the compressed 4x10 model: This model maintains 40 weekly hours, so FLSA overtime is unchanged for federal purposes. However, California's daily overtime rule means non-exempt California employees working 10-hour days will have 2 hours of daily overtime each day, which changes the pay calculation significantly. US employers with California operations should model the actual payroll cost before implementing 4x10 schedules.

Communicating the Four-Day Week to Employees and Stakeholders

How the four-day week is introduced significantly affects employee reception, client confidence, and board support. A poorly managed announcement — where employees hear contradictory information, don't understand the rationale, or fear the change is secretly a cost-cutting measure — creates anxiety and resistance that undermines the pilot before it begins.

Effective communication covers four audiences with different concerns:

Employees

Focus on what this means for them practically: which day off, whether all teams are included, whether pay is maintained, what the expectations for output are, and what happens if the pilot doesn't succeed. Answer the practical questions before they have to ask.

Managers

Managers need additional communication and training. They will field all the employee questions and must navigate the operational redesign. Equip them with clear guidance, authority to make schedule decisions for their team, and explicit support from leadership to say no to non-essential meetings.

Clients and customers

For customer-facing teams, proactive communication about availability, response time commitments, and emergency escalation paths prevents the four-day week from creating service quality anxiety. Many clients accept or welcome the change when given clear guidance; surprises create risk.

The framing of the communication matters. Positioning the four-day week as an experiment — "we're running a pilot to see whether this model works for our context" — is both honest and strategically sound. It sets the expectation that success criteria exist, that the organisation will evaluate the data, and that the decision to continue will be evidence-based. This framing protects the organisation if the pilot is unsuccessful and reinforces the message that output quality remains the primary metric.

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Frequently Asked Questions

Does a four-day work week mean 32 hours or 4x10 hours?

There are two models: the 100-80-100 model (100% pay, 80% of the time, 100% output), which is 32 hours over four days; and the compressed 4x10 model which keeps total hours at 40 but compresses them into four longer days. Research from the Icelandic and UK trials primarily applies to the 32-hour model.

Does the FLSA require overtime for a 4x10 schedule?

Under the FLSA, overtime is triggered at 40 hours per week for non-exempt employees, not per day. A 4x10 schedule that totals 40 hours per week does not trigger federal overtime. However, some states (notably California) require daily overtime for hours worked beyond 8 in a single day.

What roles are hardest to transition to a four-day week?

Customer-facing roles with five-day coverage requirements, roles with external SLAs tied to five business days, and roles requiring real-time collaboration with clients in different schedules are the hardest to transition. These require either coverage rotation, client communication adjustments, or exemption from the program.

How long should a four-day work week pilot run?

Most experts recommend a minimum 6-month pilot to capture enough data to separate novelty effects from sustainable performance change. Shorter pilots tend to show inflated positive results because employees are energized by the change itself.

What happens to benefits and PTO under a four-day work week?

Under a 32-hour model, review whether PTO accrual is calculated in hours or days. If PTO is accrued in days and employees work 4-day weeks, a 'day' of PTO covers less time relative to a five-day week, which may require policy adjustment. Benefits are generally unchanged as they are tied to employment status, not hours worked.