Data reviewed: 20 October 2026 · Engineering Desk Tools · How we check calculations
How to read a cable gland size
A cable gland has two separate sizes: the entry thread (M20, M25, M32… or the PG / NPT equivalent) that screws into the enclosure, and the cable range it can seal on. Gland makers use codes such as 20S, 20, 25S and 25: all 20-size glands have an M20 thread, but the “S” (small) version seals on a smaller cable. That is why you choose a gland from the cable diameter, not from the conductor size alone.
Metric cable gland size chart (mm)
Typical ranges for industrial brass glands (CMP A2 unarmoured, CW single-seal armoured). Ranges vary slightly between makers; always confirm with the gland maker’s selection table.
Cable gland size by armoured cable size (sq mm)
For standard BS 5467 XLPE/SWA/PVC copper cables, the cable maker lists the outer diameter and the gland size below. Use the selector above for 2, 5 and multi-core control cables.
Source: Eland Cables BS 5467 technical data (nominal diameters). Cables made to other standards, aluminium cables and Indian IS 7098 cables have different diameters – measure them or use the datasheet.
Single vs double compression cable glands
- Single compression: one seal on the outer sheath plus an armour clamp. Used indoors and in dry areas.
- Double compression: an extra seal on the inner sheath (bedding) as well as the outer sheath. Better moisture protection and cable retention; common outdoors, in wet or dusty areas and in many oil, gas and power plant specifications.
- Unarmoured glands: a single seal on the cable sheath, no armour clamp. Often nylon (PG or metric) for control panels.
PG gland size chart
PG threads (DIN 40430) are still common on European control panels. They are not interchangeable with metric threads; use an adaptor or the matching gland. Cable ranges are typical for nylon PG glands and vary by maker.
How to measure a cable for a gland
- Measure the outer sheath diameter with a vernier caliper in two directions and use the larger value.
- For a double-seal armoured gland, strip a short length and measure the inner sheath (bedding) diameter under the armour.
- Note the armour wire diameter, typically 0.9 to 2.5 mm for SWA cables.
- Check the entry on the enclosure: hole size or thread (M, PG or NPT) and wall thickness.
Cable gland questions
How do you choose a cable gland size?
Measure the cable outer diameter (and, for armoured cable with a double-seal gland, the inner sheath diameter). Pick the gland whose outer-seal range includes your diameter, check that the armour wire size is within the gland’s armour range, then choose the entry thread (metric, PG or NPT) that matches the enclosure.
What size gland for a 150 sq mm cable?
A 3-core 150 mm² BS 5467 copper SWA cable is about 45.5 mm across, which fits a 50S (M50) armoured gland; a 4-core 150 mm² cable is about 51.4 mm and takes a 50 (M50) gland. Aluminium and Indian IS 7098 cables have different diameters, so measure or check the cable datasheet.
What size gland for a 95 sq mm cable?
A 3-core 95 mm² BS 5467 SWA cable is about 37 mm across and takes a 40 (M40) gland; a 4-core 95 mm² cable is about 41.7 mm and takes a 50S (M50) gland.
What is the difference between single and double compression cable glands?
A single compression gland seals on the outer sheath only and clamps the armour. A double compression gland has a second seal on the inner sheath (bedding), giving better protection against moisture and better cable retention; it is the usual choice outdoors, in wet areas and in many industrial specifications.
What does M20 mean on a cable gland?
M20 is the metric entry thread: a 20 mm outside-diameter thread with 1.5 mm pitch that screws into a 20 mm hole or threaded entry. The cable range is separate, so two M20 glands (for example 20S and 20) can accept different cable diameters.
Are PG and metric glands interchangeable?
No. PG (Panzergewinde) threads have a different diameter and pitch from metric threads, so a PG gland will not fit a metric hole and vice versa. Use a thread adaptor or the matching gland thread for the enclosure.