Cable Gland Size Chart: 1.5 mm² to 400 mm² (Metric, PG, NPT)

Cable gland sizing confuses a lot of buyers because the gland is named after its thread (M20, PG16, 1/2″ NPT) but is actually selected by the outer diameter of the cable it clamps. A “cable gland size chart” only works once you accept this rule: conductor cross-section (1.5 mm², 185 mm²…) tells you the approximate cable OD, and the cable OD tells you the gland. This guide gives you the full mapping from 1.5 mm² to 400 mm² conductors across Metric, PG and NPT thread systems, plus panel hole sizes and the mistakes that cause leaks and failed IP68 tests.

How Cable Gland Sizing Actually Works

Every cable gland has three dimensions that matter, and only one of them is printed in the product name:

• Thread size (M20, PG16, NPT 3/4″) — how the gland fixes into the enclosure wall.
• Clamping range — the min/max cable OD the sealing insert can grip. This is the real selection criterion.
• Panel hole / drill size — the cutout needed in the enclosure wall for the thread plus locknut.

The gland does not care how many conductors are inside the cable or their cross-section; it only grips the jacket. Conductor area matters indirectly — more copper means a bigger cable and a bigger jacket. That is why the tables below map conductor size to typical OD, and you must confirm with your actual cable’s OD before ordering.

Metric (M) Thread Gland Size Chart: 1.5 mm² to 400 mm²

Metric glands follow ISO metric threads with a 1.5 mm pitch (M20×1.5, M25×1.5…). They are the default in IEC markets — Europe, the Middle East, Asia and Australia. The chart below maps common conductor cross-sections (multi-strand copper, unarmoured control or power cable) to typical overall OD and the gland that clamps it:

Values are indicative for unarmoured 4-core control and power cables. A 3-core, single-core or armoured cable of the same conductor size can be several millimetres different in OD — always check the cable datasheet and match it to the gland’s clamping range, not to this table alone.

For large single cables entering an enclosure — 185 mm² and above — a wide-range large-diameter metal cable gland such as the M32A stainless series family is the usual choice, because the long clamping seal holds heavy cable weight without crushing the insulation.

PG Thread Gland Size Chart (DIN 40430)

PG (“Panzer-Gewinde”) threads are an older German standard still extremely common on control cabinets, junction boxes and sensors shipped to markets where German equipment is installed. PG gland sizes are fixed by DIN 40430, and the thread outside diameter also tells you the panel hole:

Need the single most common PG size in depth — thread dimensions, hole size, drill diameter and wrench torque for PG9 specifically? See the PG9 cable gland specification guide, which covers the gland that fits the 4–8 mm cables used by most sensors and small control boxes.

NPT Thread Gland Sizes

NPT glands (ANSI/ASME B1.20.1 taper thread) dominate North American panels and any export project where the enclosure follows UL practice. NPT is a tapered thread, so sealing relies on thread engagement plus sealant or an O-ring, and the gland body is sized in inches:

A useful cross-reference habit for mixed projects: size the gland by cable OD first, then convert to whichever thread system the enclosure uses. The clamping insert stays the same; only the thread body changes.

Working the Other Direction: From Conductor Count to Gland

Buyers often ask “what gland fits a 4-core 10 mm² cable?” — the query behind many size searches. The safe procedure is:

1. Get the cable’s actual OD from the datasheet (a 4-core 10 mm² typically lands at 14–17 mm; 3-core versions are slimmer).
2. Pick the gland whose clamping range covers that OD with margin at both ends.
3. Only then pick the thread (M/PG/NPT) to match the enclosure knockouts.

For example, a 4-core 185 mm² cable usually has an OD near 40–46 mm, which is why “185 sq mm cable gland size” searches land on M63 or PG48 glands. A 400 mm² single-core lands closer to 55–62 mm, needing M75/M80. If the OD falls between two glands, choose the larger one and verify the seal can still compress — a gland gripped below its minimum range will leak, and one forced above its maximum will crack the seal insert.

Panel Hole and Drill Sizes for Metric Glands

When you drill the enclosure instead of using pre-made knockouts, use the hole the locknut needs — not the thread’s minor diameter:

Deburr the hole, keep the sealing gasket flat against the wall, and torque the locknut against the gland body — an over-torqued plastic gland deforms the thread; an under-torqued metal gland lets the gland rotate and loosen the cable seal. For material and IP trade-offs between nylon, brass and stainless bodies, the cable gland types overview breaks down when each body material is worth the cost.

Common Sizing Mistakes

• Ordering by thread alone. “M20 gland” is not one product — clamping ranges on M20 bodies vary from 4.5–10 mm to 9–17 mm depending on the manufacturer.
• Ignoring conductor count. The same 25 mm² conductor changes OD by 5+ mm between 3-core and 4-core constructions.
• Armoured vs unarmoured. SWA and braided cables need glands with armour termination and a different clamping section; an unarmoured gland will not stop the armour from pulling through.
• Thread system mismatch. PG threads will not seal into metric knockouts and vice versa — adaptors exist but cost more than ordering correctly.
• Skip the IP check. A correctly sized gland can still fail IP68 if the O-ring, flat gasket or locknut torque is wrong. Follow the waterproof cable gland installation notes when ingress protection matters.

자주 묻는 질문

What size cable gland do I need for a 4-core 185 sq mm cable?

Typically M63 metric or PG48, because the cable OD of a 4-core 185 mm² cable sits around 40–46 mm. Confirm with the actual cable OD and the gland’s clamping range before ordering.

Is gland size based on cable OD or conductor size?

Always cable OD. The gland’s sealing insert grips the jacket, so the clamping range must cover the actual OD. Conductor size is only a proxy for estimating OD.

What is the difference between M20 and PG16 glands?

Both clamp similar cables (roughly 6–13 mm OD), but the threads are incompatible: M20 is a 1.5 mm pitch metric thread, PG16 is a DIN 40430 thread with 22.5 mm OD. Match the thread to the enclosure knockout, not the cable.

What hole do I drill for an M25 cable gland?

About 33 mm — the hole must accept the gland body plus locknut. Always deburr and keep the flat sealing gasket in place to maintain the IP rating.

Can one cable gland size cover several cable types?

Yes, if their ODs fall inside one clamping range. Many projects standardise on M20 and M32 bodies with different seal inserts rather than ordering a new thread size per cable.