Every garment factory reports an efficiency figure, and most owners have at some point looked at a line reported at seventy per cent and wondered why the shipment is still late. What you want from the number is simple: to know how well each line is using its people's time, to compare lines and days fairly, and to see where the rest of the time went so you can recover it. This article shows how the figure is calculated, where it usually goes wrong, and how to collect the data so it tells you something you can act on.
The one idea behind the number: standard minutes
Efficiency in a garment factory compares the work a line produced with the time it had. To do that, the work has to be expressed in time. That is what the standard minute value does.
Each operation on a garment — attaching a collar, setting a sleeve, hemming — is given a standard time: the time a qualified operator, working at a normal pace with the right method, should need to complete it once, including allowances for fatigue and personal needs. It is established by work measurement, usually time study, and the method is set out in the International Labour Organization's reference text on work study. Add the standard times of all the operations on a garment and you have its standard minute value, called SMV in some factories and SAM (standard allowed minutes) in others. They mean the same thing.
A shirt with an SMV of 12 represents twelve minutes of standard work, whichever line makes it.
The calculation
The convention used across the apparel industry is:
Efficiency % = (pieces produced × SMV) ÷ (operators × minutes worked) × 100
The top line is the standard minutes the line produced. The bottom line is the minutes the line had available. The ratio is how much of the available time turned into standard work.
A worked example — the figures are illustrative, not from a particular factory:
- A line of 30 operators works a 480-minute shift.
- It makes a shirt with an SMV of 12.
- It produces 720 shirts.
Standard minutes produced: 720 × 12 = 8,640. Minutes available: 30 × 480 = 14,400. Efficiency: 8,640 ÷ 14,400 × 100 = 60%.
The same formula works for one operator on one operation: the pieces they completed multiplied by that operation's standard time, divided by the minutes they worked.
Where the number usually goes wrong
The arithmetic is easy. The inputs are where factories get figures that look precise and mean little.
- An SMV that does not belong to this style. A standard copied from a similar garment, or set years ago and never revised after a method changed, makes every efficiency figure on that style wrong in the same direction. Check that each style's SMV comes from its own operation breakdown.
- Who counts as an operator. Some factories count only machine operators, others include helpers, ironers and checkers. Either can be defended; mixing them between lines or months cannot. Write down the rule and keep it.
- Which minutes count. Decide whether breaks, meetings and changeover time are in the denominator, and keep the decision the same everywhere.
- Where output is counted. Output counted at the end of the line is what matters for shipment. Output counted per operation can make a line look busy while unfinished work piles up in the middle of it.
- Comparing different styles. A line on a simple style and a line on a complex one can report the same efficiency while one is in trouble. Compare a line with itself on the same style, or compare against each style's own target.
- Piece-rate records used as output. If operators are paid by the piece, the tickets they submit are a pay record first. They are useful, but they are not a neutral count.
Separate the time the line could not use
The most useful thing you can do with efficiency is split it into two figures.
- Overall efficiency uses every minute the operators were present.
- On-standard efficiency removes the minutes they could not work for reasons outside their control — waiting for cut panels, a machine breakdown, no trims, a style change.
In the example above, suppose the line lost 60 minutes of the shift, across all 30 operators, waiting for cut pieces from the cutting room. That is 1,800 operator-minutes. On-standard efficiency is then 8,640 ÷ (14,400 − 1,800) × 100, about 69%.
The gap between 60% and 69% is not the sewing line's performance. It is the cutting room's, or the planner's, and it is exactly the time a factory can recover without asking anyone to sew faster. Without a record of lost time and its reasons, that gap is invisible and the sewing supervisor carries the blame for it. Paper, WhatsApp and old Windows programs: how garment factories lose production time looks at why that lost time so often goes unrecorded.
Efficiency is not the same as productivity
Efficiency tells you how well the time was used against a standard. Productivity measures output against input directly — pieces per operator per hour, for instance. Productivity is easier to understand and harder to compare across styles; efficiency is comparable across styles only if the standards are right. Use efficiency to manage lines and productivity to talk about capacity, and do not mix them in one report.
What to record, every day
You need very little to get an efficiency figure you can trust.
- Hourly output per line, counted at the end of the line, against an hourly target.
- Attendance per line, by the rule you chose for who counts.
- Lost time, with a reason and a duration: waiting for work, machine down, no material, style change, quality hold.
- The style on the line, with its SMV.
Recorded on paper and typed up later, these arrive a day late and are rarely complete. Recorded at the line as they happen, they give you efficiency by the hour and let a supervisor act before the shift is over. That is also how you find the operation that is holding the line back; finding the bottleneck on a sewing line picks up from there.
The next step
For one week, record lost time and its reasons on one line, alongside its output and attendance, and calculate both overall and on-standard efficiency each day. The difference between the two is the time your factory can win back first. Softwiro builds production tracking for factories, so these numbers can come from the floor as work happens rather than from a spreadsheet the next morning — tell us how your lines are measured today.
Sources
- Introduction to Work Study, fourth revised edition — International Labour Office. Work measurement, time study and the computation of standard time.
- Lean Manufacturing Techniques for the Ready-Made Garments Industry — International Labour Organization, Cairo office. Line balance, bottlenecks and waste on garment lines.
- What are the 7 wastes in lean? — Lean Enterprise Institute. Waiting and other time losses on a production floor.