Sewing line efficiency calculator
How many standard minutes the line earned, compared with the minutes its operators were available. The definition of 'available' is stated, so the result can be compared with your own reports.
How this is calculated
earned minutes = good pieces × SMV and available minutes = operators × working minutes. Efficiency is earned ÷ available × 100. Working minutes are paid attendance on the line, excluding scheduled breaks.
If you enter off-standard operator-minutes, the calculator also reports on-standard efficiency = earned ÷ (available − off-standard) × 100.
Worked example. 30 operators work 480 minutes and produce 600 good pieces of a 12-minute garment. Earned minutes = 600 × 12 = 7,200. Available minutes = 30 × 480 = 14,400. Efficiency = 7,200 ÷ 14,400 = 50.0%. With 720 operator-minutes of recorded breakdown, on-standard efficiency is 7,200 ÷ 13,680 = 52.6%.
Questions
- Which operators belong in the available minutes?
- Everyone whose work is included in the SMV. If the operation bulletin includes helper operations (trimming, bundling), count those helpers; if it does not, leave them out. Mixing the two definitions is the most common reason two factories report very different efficiencies for the same performance.
- Should rejected or reworked pieces count as output?
- Count only good pieces that passed end-line inspection. Counting rework twice, or counting pieces that will be rejected, inflates earned minutes and hides a quality problem as a productivity gain.
- What is on-standard efficiency?
- Efficiency calculated after removing off-standard time the operators could not control - machine breakdown, waiting for cut panels, meetings. It shows how well the line worked while it had work. Report both figures: overall efficiency is what costing depends on.
- Can efficiency be above 100%?
- Yes, arithmetically. It means the line produced more standard minutes than the minutes it was present. In practice a sustained figure above 100% usually means a loose SMV, a miscount of operators, or output that includes rework - check those before treating it as real.
Sources & verification
Earned (standard) minutes and their ratio to time worked are the basic productivity measures of work measurement described in the ILO's Introduction to Work Study (Kanawaty, ed., 4th ed., 1992). The worked example above is recomputed in the site's automated tests.