In factories where every second counts, time studies are essential for defining standard work and optimizing labor efficiency. But what often goes unnoticed is the hidden cost of unfair expectations. If time standards ignore the human element—fatigue, recovery, micro-delays—they become unrealistic and even dangerous. That’s where ISO 6385 steps in. This international standard establishes the fundamental ergonomic principles for designing work systems that are not only productive but also safe and humane. 

In this blog, we’ll explore why ISO 6385 is essential for setting fair allowances in time studies—and what happens when it’s ignored.

The Foundation: What Is ISO 6385? 

ISO 6385 is the international standard titled “Ergonomic principles in the design of work systems.” Developed by the International Organization for Standardization, it provides a comprehensive framework for designing work environments that respect human physical and cognitive limits.

Unlike task-specific guidelines, ISO 6385 is a foundational standard—used to align all workplace design, including job roles, processes, tools, and timings, with ergonomic principles. It doesn’t dictate exact numbers or limits; instead, it guides organizations to ensure that work design is human-centered, sustainable, and efficient.

In time studies, where tasks are broken into elements and timed using methods like stopwatch timing or Predetermined Motion Time Systems (PMTS), ISO 6385 becomes crucial. Why? Because raw timing only reflects the ideal pace—not real-world conditions. ISO 6385 legitimizes the use of standard allowances that reflect fatigue, delays, and personal needs, ensuring fairness in how labor expectations are set.

This is especially important in high-precision or high-volume industries like automotive, electronics, and aerospace, where even a few seconds of unfairness multiplied over thousands of cycles creates not only inefficiency but systemic worker dissatisfaction.

The Role of Allowances: Not Extra Time, But Essential Time

In time studies, allowances are adjustments added to the basic time (observed time × performance rating) to reflect real-world working conditions. These are not “buffers” or “slack time”—they are scientifically justified additions necessary to protect worker health, performance consistency, and operational sustainability.

Types of Common Allowances

By integrating these allowances, the resulting Standard Time becomes more than just a productivity metric—it becomes a fair benchmark that acknowledges the realities of human work.

ISO 6385 ensures that these allowances are not arbitrarily applied. Instead, it promotes a systematic, documented, and justifiable approach, which is especially critical in unionized environments or where labor laws scrutinize work conditions.

How to Integrate ISO 6385 Into Time Study Practice?

Integrating ISO 6385 into your time study process isn’t just about meeting a compliance checkbox—it’s about embedding a mindset of fairness, human performance, and operational sustainability into every work standard you create. Here’s how to make ISO 6385 practical and actionable in your time study efforts:

1. Begin with Work Design, Not Stopwatch Timing

Before collecting any timing data, evaluate the design of the task itself. ISO 6385 emphasizes the importance of designing work systems that fit human capabilities and limitations. Ask:

• Is the motion repetitive or fatiguing?
• Does the work posture create ergonomic strain?
• Are tools and materials located within optimal reach zones?
• Are environmental conditions—like heat, noise, lighting, or required PPE—adding to fatigue?

If the task is poorly designed, even the most accurate time study will yield flawed standards. Read our blog to learn how standard work helps in achieving ISO requirements. 

2. Use Predefined, Defensible Allowance Models

ISO 6385 legitimizes the use of allowances, but it doesn't prescribe exact percentages. To translate principles into numbers, use widely accepted references like:

• BS 3138 for fatigue and contingency allowance recommendations
• ILO guidelines for personal needs time
• Industry-specific ergonomic studies or national labor standards

Establish a clear, documented allowance structure for fatigue, personal needs, and unavoidable delays. Avoid ad-hoc or subjective decisions—consistency is key to fairness and auditability.

3. Actively Involve Workers and Supervisors

In line with ISO 6385’s participatory approach, involve the people closest to the work:

• Ask operators about what makes the task mentally or physically tiring.
• Collect input from supervisors on recurring delays, machine readiness, and changeover issues.
• Involve safety or ergonomics teams to assess physical demands.

This not only improves the accuracy of allowances but also strengthens trust and buy-in from the workforce.

4. Document All Assumptions and Decisions

A core ISO 6385 principle is transparency. A compliant time study should include:

• Method used (e.g., stopwatch, PMTS)
• Performance rating and justification
• Allowance percentages and their sources
• Notes on ergonomic or environmental conditions

This documentation serves as a defense in audits, labor negotiations, and internal reviews. It also creates a knowledge base for future improvement.

5. Leverage Digital Tools to Operationalize ISO 6385

Manual time study documentation is error-prone and hard to scale. Tools like Solvonext help teams:

• Apply ISO 6385-aligned allowance structures automatically
• Embed ergonomic notes and photos
• Standardize performance ratings across analysts
• Make standards visible, editable, and trackable in real-time

Digitalization bridges the gap between ergonomic intent and real-world execution—making ISO 6385 truly actionable at scale.

Conclusion: ISO 6385 Turns Time Studies into Ethical Standards

Time studies are powerful tools—but without ergonomic principles, they risk becoming exploitative. ISO 6385 ensures time standards are not only efficient but fair, ethical, and sustainable. It brings structure to the often-overlooked practice of setting allowances, grounding them in human physiology, not guesswork. When you apply ISO 6385, you move from stopwatch-based pressure to people-centered performance. This shift doesn’t just improve compliance—it builds trust, reduces injuries, and drives long-term productivity.

For factories aiming to standardize work without overburdening teams, ISO 6385 isn’t optional—it’s essential.

Want to embed ergonomic fairness into your time studies?

Try Solvonext, a digital tool built to operationalize ISO standards and make continuous improvement people-first.