What is Line Capacity
Line capacity is the number of pieces a line can produce in a given period, such as per day or per month. It is the foundation of order booking, delivery commitment, and resource planning.
Basic Formula
Line capacity equals number of machines times working hours times efficiency divided by SMV of the style. Working hours are converted to minutes. Efficiency is expressed as a decimal.
Practical Example 1 — Basic Calculation
A line has 25 machines, works 8 hours per day, has 65 percent efficiency, and the style SMV is 5 minutes. Capacity equals 25 times 480 times 0.65 divided by 5 equals 1560 pieces per day.
Practical Example 2 — Monthly
If the line works 26 days per month, monthly capacity is 1560 times 26 equals 40,560 pieces per month.
Practical Example 3 — Style Change
New style SMV is 8 minutes. Capacity equals 25 times 480 times 0.65 divided by 8 equals 975 pieces per day. The planner must update the capacity number when the style changes.
Practical Example 4 — Efficiency Variation
The same line has 65 percent efficiency in early weeks and 80 percent after ramp-up. Capacity rises from 1560 to 1920 pieces per day. Planners must use the correct efficiency figure for the correct period.
Adjustments for Real Capacity
Real capacity is lower than theoretical because of absenteeism, downtime, and quality issues. A common rule is to multiply by a realistic efficiency (from history) and subtract planned absenteeism.
Common Mistakes
Using 100 percent efficiency. Ignoring absenteeism. Using one SMV for all styles. Not updating after method improvements. Not checking on the floor.
How to Use the Number
Match order booking to capacity plus buffer. Plan style allocation with capacity in mind. Quote realistic delivery dates using capacity. Review capacity monthly and adjust.
When to Use It
Capacity calculation is done at the start of every order, every style change, and every month in the planning cycle. It is the single most important number in production planning.