Calculator Inputs
Example Data Table
| Task | Time (sec) | Immediate Predecessor |
|---|---|---|
| A | 35 | None |
| B | 20 | None |
| C | 40 | A |
| D | 25 | A |
| E | 30 | B |
| F | 15 | C |
| G | 28 | D |
| H | 22 | E |
Example scenario: 480 minutes available, 90% net availability, 120 units required, and 5% demand buffer.
Formula Used
1. Raw Takt Time
Raw Takt = Gross Available Time ÷ Required Output
2. Net Available Time
Net Available Time = Gross Available Time × Net Availability Rate
3. Adjusted Demand
Adjusted Demand = Required Output × (1 + Demand Buffer)
4. Design Cycle Time
Design Cycle Time = Net Available Time ÷ Adjusted Demand
5. Total Task Time
Total Task Time = Sum of All Task Times
6. Theoretical Minimum Stations
Minimum Stations = Ceiling(Total Task Time ÷ Design Cycle Time)
7. Line Efficiency
Efficiency = Total Task Time ÷ (Actual Stations × Design Cycle Time) × 100
8. Balance Delay
Balance Delay = 100 − Efficiency
9. Total Idle Time
Total Idle Time = (Actual Stations × Design Cycle Time) − Total Task Time
10. Smoothness Index
Smoothness Index = √Σ(Design Cycle Time − Station Load)²
How to Use This Calculator
- Enter total production time for the planning period.
- Select the matching time unit for that period.
- Enter the output demand you must achieve.
- Set net availability to reflect downtime, meetings, breaks, and losses.
- Add a demand buffer if you want a safer design target.
- Select the task time unit and enter each task on a new line.
- Add precedence rules if tasks must happen in sequence.
- Optionally enter planned stations for scenario comparison.
- Press the calculate button to see summary metrics, station allocations, and the chart.
- Use CSV or PDF export to save the result for planning reviews.
Frequently Asked Questions
1. What does assembly line balance measure?
It measures how evenly work is distributed across stations relative to the target cycle time. It also reports efficiency, idle time, delay, station count, and likely bottlenecks.
2. Why is cycle time so important?
Cycle time sets the maximum workload a station should carry if the line must hit target output. If stations exceed it, the line will struggle to meet required production.
3. What happens if one task exceeds cycle time?
That task cannot fit into any feasible station under the current production target. You should split the task, increase available time, reduce demand, or improve the method.
4. How do precedence rules affect balancing?
Precedence rules force certain tasks to occur before others. They reduce assignment flexibility, which can increase station count, idle time, and smoothness variation across the line.
5. Why can efficiency look low even with enough stations?
Efficiency drops when station loads are uneven or when extra stations are included for planning. Idle capacity grows whenever actual station time falls far below cycle time.
6. What does the smoothness index mean?
It shows how far station workloads deviate from the target cycle. Lower values indicate a more even balance, while higher values signal stronger imbalance and possible bottlenecks.
7. Should I use gross or net available time?
Use gross time first, then apply a realistic availability rate to create net available time. Net time better reflects what the line can truly deliver under normal conditions.
8. Can I use this tool for scenario planning?
Yes. Adjust demand, availability, buffer, and planned stations to compare scenarios. This helps test staffing, line redesign, and output commitments before changing the floor plan.