Like individual operator efficiency, efficiency of a production line or batch or section is important for a factory. Daily line efficiency shows the line performance. To calculate efficiency of a line for a day, you will need following data (information) from the line supervisor or line recorder.
1. Number of operators – how many operators worked in the line in a day
2. Working hours (Regular and overtime hours) – how many hours each of the operators worked or how many hours the line run in a day
3. Production in pieces – How many pieces are produced or total line output at the end of the day
4. Garment SAM – What is exact standard minute of the style (garment)
Once you have above data you have to calculate following using above information 
a. Total minutes produced by the line: To get total produced minutes multiply production pieces by SAM
b. Total minutes attended by the all operators in the line: Multiply number of operators by daily working hours and convert total hours into total minutes (multiplying by 60).
Now, calculate line efficiency using following formula:
Line efficiency (in percentage) = Total minutes produced by the line *100 /total minutes attended by all operators
For example, refer following table. Data calculation formula has been given on the header row of the table.
1. Number of operators – how many operators worked in the line in a day
2. Working hours (Regular and overtime hours) – how many hours each of the operators worked or how many hours the line run in a day
3. Production in pieces – How many pieces are produced or total line output at the end of the day
4. Garment SAM – What is exact standard minute of the style (garment)
Once you have above data you have to calculate following using above information 
a. Total minutes produced by the line: To get total produced minutes multiply production pieces by SAM
b. Total minutes attended by the all operators in the line: Multiply number of operators by daily working hours and convert total hours into total minutes (multiplying by 60).
Now, calculate line efficiency using following formula:
Line efficiency (in percentage) = Total minutes produced by the line *100 /total minutes attended by all operators
For example, refer following table. Data calculation formula has been given on the header row of the table.
No. of
Operator (A) 
Working
hours (B) 
line output
(production) (C) 
Garment
SAM (D) 
Total
minutes
attended (E=A*B*60) 
Total Minute
produced (F=C*D) 
Line
Efficiency (%) (F/E*100) 
48

8

160

44.25

23040

7080

30.73

48

11

240

44.25

31680

10620

33.52

34

8

300

25

16320

7500

45.96

35

11

400

25

23100

10000

43.29

35

11

329

25

23100

8225

35.61

34

8

230

25

16320

5750

35.23

34

8

200

35

16320

7000

42.89

35

11

311

35

23100

10885

47.12

34

11

340

35

22440

11900

53.03

Related Topics:
How to calculate SAM for a garment?
Garment CM cost estimation using SAM or SMV
The Concept of Operator's Performance Rating
How to calculate operator efficiency at work?