To fulfill its function, especially tear strength and ingress protection, cable gland must be adapted to the diameter of the cable.
This diameter is a function of several parameters: the number of conductors, electrical power, voltage insulation, cable length and type of mechanical protection depending its application
The selection must be done in 3 steps

Step 1: selection of cable Gauge, upon power and maximum length of cables, single phase and three phase.

Gauge, mm² Single phase 230V, power factor =1 3 phase, power factor = 0.8
Power (kw) Electrical rating,
(A)
Maximum cable
length, with voltage
drop less than 3%
(m)
Power (kw) Electrical rating,
(A)
Maximum cable
length, with voltage
drop less than 5%
(m)
1.5 1 4.6 50            
1.5 6.8 33
2 9 25
2.5 11.5 20 2.5  5  190
3 13.5 17 3 160 
3.5 16 14 3.5 135 
                  4 120 
4.5 105 
 5 10  96 
12  79 
14  68 
8 16 60
9 18 51
2.5 1 4.6 84
1.5 6.8 57
2 9 43
2.5 11.5 34 2.5 5 325
3 13.5 29 3 6 270
3.5 16 24 3.5 7 230
4 18 21 4 8 200
4.5 20 19 4.5 9 180
5 10 165
6 12 135
7 14 115
8 16 105
9 18 92
10 19 84
12 23 69
4 1 4.6 135
1.5 6.8 90
2 9 88
2.5 11.5 54 2.5 5 510
3 13.5 45 3 6 420
3.5 16 39 3.5 7 365
4 18 34 4 8 320
4.5 20 30 4.5 9 285
5 23 27 5 10 255
6 27 23 6 12 210
7 14 180
8 16 160
9 18 145
10 19 130
12 23 110
14 27 94
16 31 81

 

Step 2: depending of application, select insulation and mechanical protection, and find cable outside diameter (Most usual flexible cables)

Gauge, mm²  H05-VVF
500V,
PVC insulation
Cable gland size H05-RRF 500V,
rubber
insulation
Cable gland size H07-RNF,
450/750 V.
Can be used in fixed installations with nominal voltages
up to 1000V: see NF G 15-100, 512.1.1.
Excellent resistance to weathering, oils and fats,
resistance to mechanical and thermal stresses, outdoor
use, hazardous areas, agricultural areas, connecting
mobile devices
Cable gland size
3 x 1 6.8 M16 8.5 M16 11.5 M20, M24
3 x 1.5 7.2 M16 10.4 M20 12.5 M20, M24
3 x 2.5 8 M16, M20 12.4 M20, M24 14.5 M24, M25
3 x 4 10 M16, M20 14.5 M24, M25 16 M24, M25
5 x 1 9.8 M16, M20 10.3 M20 13.5 M24, M25
5 x 1.5 11.6 M20, M24 12.7 M20, M24 15 M24, M25
5 x 2.5 13.9 M24, M25 15.3 M24, M25 17 M25
5 x 4 16 M24-M25

Step 3: select cable gland size upon its internal diameter ranges (standard models used in this catalogue)

Models M16 M20 M24 M25
Min and max dia. 6-10 8-13 11-16 13-18