The 4-day work week is a working time model in which employees work four instead of five days per week – either with compressed hours (40 hours across 4 days) or reduced hours (32 hours at full pay following the 100-80-100 principle). According to the German pilot study by the University of Münster (2024), 73% of participating companies continued the model after the test phase, as employee satisfaction and health improved without any decline in productivity or revenue. In Germany, the 4-day work week is currently mentioned in only about 0.12% of job postings – making it a strategic differentiator in recruiting.
Definition: What Is the 4-Day Work Week?
The 4-day work week refers to a working time model in which employees distribute their weekly working hours across four instead of five days. Unlike traditional part-time work, full salary may be maintained depending on the model.
The concept aims to improve work-life balance while maintaining or even increasing productivity. The underlying idea: well-rested employees work more focused and efficiently. Internationally, the model has gained attention through pilot projects in the UK, Iceland, and Belgium. In Germany, 45 companies tested the 4-day work week for the first time in 2024 under the scientific supervision of the University of Münster.
Overview of 4-Day Work Week Models
There is no single "4-day work week." Depending on the design, the models differ significantly in working hours, salary, and productivity expectations.
The 100-80-100 Model (Reduced Hours, Full Pay)
Under the 100-80-100 model, employees receive 100% of their salary for 80% of working time – with the expectation of delivering 100% of their previous output. In practice, this typically means a reduction from 40 to 32 weekly hours.
This model was developed in 2018 by Charlotte Lockhart and Andrew Barnes in New Zealand and has since been promoted internationally by the organization "4 Day Week Global." It requires companies to optimize their processes, reduce meetings, and minimize distractions. The 2024 German pilot study primarily tested this model.
The Belgian Model (Compressed Working Hours)
Since 2022, employees in Belgium have had a legal right to compress their full weekly working hours into four days. With a 40-hour week, this means 10 hours per working day.
Salary remains unchanged since working hours stay the same – they are simply distributed differently. In practice, however, this model is used less than expected, as many employees find the long working days burdensome.
Part-Time Variant (Reduced Hours and Reduced Pay)
The traditional variant involves reducing to four working days with correspondingly adjusted salary – effectively a part-time position with 32 instead of 40 hours at 80% of the previous salary.
According to a Randstad/ifo survey (2024), 47% of companies with a 4-day work week offer this part-time variant, 43% maintain full salary with compressed working hours (Belgian model), and only about 1.1% implement the 100-80-100 model with full wage compensation for reduced working hours.
Legal Framework in Germany
Working Hours Act and Maximum Working Time
The 4-day work week is fundamentally legal in Germany – there is no law prohibiting it. However, the provisions of the Working Hours Act (Arbeitszeitgesetz, ArbZG) must be observed.
According to §3 ArbZG, maximum working time is 8 hours per working day. It can be extended to up to 10 hours if an average of 8 hours per working day is maintained within 6 months or 24 weeks.
This means: The Belgian model with 10-hour days is legally possible but requires appropriate compensation. A permanent 10-hour arrangement without compensation would not be permissible.
Vacation Entitlement with the 4-Day Work Week
The statutory minimum vacation entitlement is based on the number of weekly working days. For a 5-day week, it amounts to 20 days (4 weeks × 5 days); for a 4-day week, it is correspondingly 16 days (4 weeks × 4 days).
The actual vacation duration in weeks remains the same – you still have at least four weeks of vacation per year. Contractual arrangements can, of course, be higher.
Employment Contract and Co-Determination
To introduce a 4-day work week, the employment contract must be adjusted accordingly. In companies with a works council, the co-determination rights under §87 BetrVG (Works Constitution Act) must also be observed, as the start and end of daily working hours and their distribution across weekdays are subject to co-determination.
Current Studies and Results
German Pilot Study by the University of Münster (2024)
The largest German study on the 4-day work week to date was conducted in 2024 by the University of Münster under the direction of Prof. Dr. Julia Backmann. 45 companies from various industries tested the model over six months.
The key findings:
Revenue and profit remained stable compared to the previous year – despite reduced working hours. Employees reported significantly less stress and improved health metrics. Average sleep duration increased by 38 minutes per week. 73% of participating companies decided to continue the model after the test phase. 20% returned to the 5-day week, and 7% were still undecided.
However, the significance is limited: the participating companies are not representative of the German economy, and the six-month duration does not allow conclusions about long-term effects.
International Experiences
Iceland tested a shortened work week for over 2,500 public sector employees between 2015 and 2019. The result: improved health and productivity with consistent output. Today, 86% of Icelandic workers have access to reduced working hours.
In the UK, around 60 companies participated in a pilot study in 2022. Most kept the model after the test and reported less stress and more time for family and recreation.
Advantages and Disadvantages for Employers
Introducing a 4-day work week brings both opportunities and challenges.
The advantages include potentially higher employee satisfaction and motivation, fewer sick days due to better recovery, a competitive advantage in recruiting (especially for younger target groups), possible energy cost savings, and stronger employer attractiveness.
On the other hand, there are challenges such as organizational complexity during implementation, potential work intensification and increased time pressure, difficult implementation in industries with fixed opening hours or shift work, possible customer service limitations, and the need for process optimization to maintain productivity.
The German Economic Institute (IW Köln, 2025) shows: Around 80% of German companies remain skeptical about the 4-day work week. Many see significant challenges in implementation, particularly rising personnel costs and difficulties in order processing.
The 4-Day Work Week as an Employer Branding Tool
Flexible working models are no longer a bonus but a hygiene factor – especially for millennials and Generation Z. According to a study by the Hans Böckler Foundation (2023), 81% of full-time employees want a 4-day work week, with 73% only wanting it with full wage compensation.
Yet the supply remains scarce: The Bertelsmann Foundation (2025) analyzed 34 million job postings and found that only 0.12% of job offers in 2024 mentioned the 4-day work week – equivalent to about 8,600 postings.
Interestingly, the model is advertised almost three times more often in shortage occupations than in occupations without skills shortages. It is particularly common in skilled trades (interior construction: 0.4%), building technology (0.32%), and medical healthcare (0.27%) – areas where other flexibility options like remote work are limited.
For HR professionals, this means: The 4-day work week can be a genuine differentiator in the competition for talent, especially in hard-to-fill positions.
Practical Implementation for HR
Introducing a 4-day work week requires careful planning. Proven steps include:
First, choose the right model: Which variant fits your company? The 100-80-100 model requires process optimization; the Belgian model means long working days. Assess what is realistic for your industry and teams.
Then consider a pilot project: Start with one team or department before rolling out the model company-wide. The German pilot study shows that adjustments during the test phase are often necessary.
Process optimization is also important: The University of Münster study shows that successful companies primarily reduced distractions (65%), optimized processes (63%), and adjusted meeting structures (52%).
Finally, ensure clear communication: Inform employees, customers, and, if applicable, the works council early on. Define clear expectations regarding availability and output.
Flexible working time models like the 4-day work week require employees with high self-responsibility and self-organization. With objective aptitude diagnostics, HR teams can make these competencies measurable and identify candidates who fit well with flexible working models and company culture.
Frequently Asked Questions About the 4-Day Work Week
What is the 4-day work week?
The 4-day work week is a working time model in which employees work four instead of five days per week. Depending on the design, weekly working hours remain the same (compressed into 4 days) or are reduced (e.g., from 40 to 32 hours). The goal is better work-life balance with consistent or higher productivity.
What is the 100-80-100 model?
The 100-80-100 model means: 100% salary for 80% of working time with 100% expected productivity. Typically, employees then work 32 instead of 40 hours per week. The model assumes that companies optimize their processes so that the same output is possible despite less working time.
Do you earn less with the 4-day work week?
That depends on the chosen model. With the 100-80-100 model and the Belgian model, salary remains the same. With the part-time variant, salary is adjusted according to reduced hours. According to surveys, about 47% of companies offer the part-time variant with wage reduction, while 43% maintain salary with compressed working hours.
How much vacation do you get with the 4-day work week?
Vacation entitlement is based on weekly working days. With 5 working days, the statutory minimum entitlement is 20 days; with 4 working days, it is correspondingly 16 days. The actual vacation duration in weeks (at least 4) remains the same – so you don't have less recovery time.
Is the 4-day work week legal in Germany?
Yes, the 4-day work week is fundamentally legal. There is no law prohibiting it. However, the Working Hours Act must be observed: The daily maximum working time of 8 hours (extendable to 10 hours with compensation) may not be permanently exceeded. The employment contract must be adjusted accordingly, and the works council may need to be involved.
What do studies say about productivity with the 4-day work week?
The German pilot study by the University of Münster (2024) shows: Revenue and profit remained stable among participating companies despite less work. 73% of companies continued the model after the test. International studies from Iceland and the UK confirm similar results. However, effects are highly industry-dependent.
Which industries are suitable for the 4-day work week?
Knowledge-based industries such as IT, creative industries, and consulting are well suited. The 4-day work week is also used above average in skilled trades – for example, with Friday as a day off. Implementation is more difficult in production, shift work, retail, and healthcare, where fixed opening hours or presence requirements exist.
How does the 4-day work week affect recruiting?
The 4-day work week is a strong employer branding tool, especially for younger target groups. Since only 0.12% of job postings mention the model, it offers a genuine differentiator. In shortage occupations, it is offered almost three times more often than in other areas – as a lever to make hard-to-fill positions more attractive.
Conclusion
The 4-day work week is neither a widespread future model nor a short-term trend. It is a strategic tool that, when implemented correctly, can offer benefits for both employers and employees: higher satisfaction, better health, and potentially consistent productivity.
For HR professionals, a differentiated view is worthwhile: Which model fits your own industry and company culture? Where are the biggest challenges? And can the 4-day work week be used as a recruiting advantage?
Current studies show: There is no "one-size-fits-all." But companies that experiment flexibly and optimize their processes can benefit from the model – and differentiate themselves in the competition for talent.
Want to find the right employees for flexible working models? The digital platform Aivy supports HR teams with scientifically validated aptitude diagnostics to objectively measure competencies like self-responsibility and self-organization. Learn more about Aivy
Sources
- Backmann, J., Hoch, F., Hüby, J., Platz, M., Sinnemann, M.F. (2024). "The 4-Day-Week in Germany: First Results of Germany's Trial on Work Time Reduction." University of Münster / Intraprenör. https://intraprenoer.webflow.io/4tagewoche
- Lott, Y., Windscheid, E. (2023). "4-Tage-Woche: Vorteile für Beschäftigte und betriebliche Voraussetzungen." WSI Policy Brief No. 79, Hans Böckler Foundation. https://www.boeckler.de/de/pressemitteilungen-2675-rund-81-prozent-der-vollzeitbeschaftigten-wollen-vier-tage-woche-49242.htm
- Bertelsmann Foundation (2025). "4-Tage-Woche: Chance für Einstieg in flexible Arbeitszeitmodelle." Jobmonitor Analysis. https://www.bertelsmann-stiftung.de/de/themen/aktuelle-meldungen/2025/november/4-tage-woche-chance-fuer-einstieg-in-flexible-arbeitszeitmodelle
- German Economic Institute (2025). "Die 4-Tage-Woche in der deutschen Wirtschaft." IW Report. https://www.iwkoeln.de/fileadmin/user_upload/Studien/Report/PDF/2025/IW-Report_2025-Vier-Tage-Woche.pdf
- Working Hours Act (Arbeitszeitgesetz, ArbZG). Federal Republic of Germany, current version. https://www.gesetze-im-internet.de/arbzg/
- Haufe (2023). "Modelle der 4-Tage-Woche: Was Unternehmen beachten sollten." https://www.haufe.de/personal/hr-management/modelle-der-4-tage-woche-was-unternehmen-beachten-sollten_80_601744.html
- 4 Day Week Global. International initiative for reduced working hours. https://www.4dayweek.com/
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