What Is a DIN Rail? Understanding the Standard

Whether you stock electrical components for panel builders or specify parts for your own projects, you deal with one piece of hardware constantly: the metal rail running across the backplate that terminal blocks, circuit breakers, relays, and power supplies all snap onto in neat rows. That rail is a DIN rail. And its dimensions are not arbitrary — getting them right matters for every customer you serve.

DIN rail traces back to 1928, when the German electrical utility RWE needed a standardized way to mount components inside equipment enclosures. The concept was later commercialized by Phoenix Contact and codified into a series of standards that evolved from the original German DIN 46277-3, through the European EN 50022, to today’s international IEC 60715 (current edition: 2017, Edition 2.0). In Germany, the corresponding national standard is DIN EN 60715 / VDE 0660-520:2018-07.

“DIN rail” does not refer to a single size. IEC 60715 defines four standard profiles, each identified by two numbers: width and height in millimeters. The 35 mm wide TS35 family accounts for over 90% of global installations. But even within TS35, two distinct depth variants serve very different purposes.

Think of DIN rail like a LEGO baseplate: a universal mechanical interface that lets components from different manufacturers — a Schneider MCB, a Weidmüller terminal block, a Siemens PLC module — all snap onto the same mounting system.

Standard DIN Rail Dimensions by Type

IEC 60715 recognizes four standard DIN rail profiles, each defined by a unique width × height combination. The TS35 series dominates modern installations; TS15 and TS32 serve specific niche applications. Below, each type is broken down with exact dimensions, tolerances, and typical use cases.

TS35 × 7.5 — The Global Standard Top-Hat Rail

When an engineer says “DIN rail” without qualification, they mean TS35 × 7.5. This is the universal default. You’ll find it in virtually every control panel, distribution board, and automation cabinet worldwide.

Exact dimensions:

• Width: 35 mm (±0.3 mm tolerance per IEC 60715)
• Height: 7.5 mm (+0 / −0.4 mm tolerance)
• Material thickness: 1.0 mm (cold-rolled steel DC01, per EN 10130)
• Weight: approximately 0.30–0.35 kg per meter (zinc-plated steel)

Typical applications:

• Miniature circuit breakers (MCBs): a standard 18 mm-wide single-pole MCB snaps directly onto TS35
• Terminal blocks: the vast majority of screw-clamp and spring-clamp terminals are TS35-compatible
• PLC I/O modules, signal conditioners, and small relays

Most perforated TS35 rails feature oblong mounting slots measuring 6.2 mm × 15 mm on 25 mm center-to-center spacing. This hole pattern is a de facto industry convention. IEC 60715 does not explicitly mandate it, but virtually every manufacturer follows it. Standard supply lengths are 1 meter and 2 meters, with custom cuts available from most suppliers.

For quick reference: one meter of TS35 × 7.5 accommodates roughly 10–12 standard single-pole MCBs (18 mm each), or about 150–200 compact terminal blocks (5–6 mm each).

TS35 × 15 — The Deep Top-Hat for Heavy-Duty Applications

Same 35 mm width, double the depth — and significantly more than double the rigidity.

Exact dimensions:

• Width: 35 mm
• Height: 15 mm
• Material thickness: 1.5 mm (some manufacturers offer 2.0–2.3 mm reinforced versions)
• Weight: approximately 0.62–0.65 kg per meter

The critical difference is structural. The 15 mm deep profile has roughly 3–4 times the section modulus of the 7.5 mm version, so it resists bending under heavy loads far better. In vibration-prone environments — machinery control cabinets on factory floors, panels inside moving equipment — TS35 × 15 is the standard choice.

When to use TS35 × 15 instead of TS35 × 7.5:

• Mounting heavy power supplies (200W and above)
• Large contactors and motor starters
• Any component weighing more than 2–3 kg individually
• Environments with continuous mechanical vibration
• When mounting screw spacing exceeds 400 mm: the deeper profile bridges longer spans without sagging

A practical rule of thumb: if you can feel the weight of the component when you pick it up with one hand, mount it on TS35 × 15.

TS15 — The Miniature Rail for Compact Spaces

TS15 is the scaled-down sibling. Same top-hat geometry, but 15 mm wide and just 5.5 mm high.

Exact dimensions:

• Width: 15 mm (±0.15 mm — tighter tolerance than TS35)
• Height: 5.5 mm (±0.1 mm)
• Material thickness: 1.0 mm
• Weight: approximately 0.14 kg per meter
• Governing standard: EN 50045 (not EN 50022)

TS15 serves compact junction boxes, building automation controllers, and miniature relay modules where a full 35 mm rail would waste valuable enclosure space. It is also common in HVAC control panels and lighting control systems.

Important compatibility note: TS15-mounted components cannot be snapped directly onto a TS35 rail. If you need to mix TS15 and TS35 devices in the same panel, you’ll need adapter brackets or separate rail sections.

TS32 (G-Section) — The Legacy Heavy-Duty Rail

TS32 is the oldest profile still in active use, dating from the pre-IEC era. Unlike the symmetrical top-hat shape, TS32 has an asymmetrical G-shaped cross-section.

Exact dimensions:

• Width: 32 mm
• Height: 15 mm
• Material thickness: 1.5 mm
• Governing standard: EN 50035

The asymmetrical G-profile provides an accidental benefit: components can only be slid on from one direction, creating natural polarity protection. You physically cannot install a device upside down. This made TS32 popular for heavy-duty contactors, large transformers, and motor starters in older European installations.

Today, most TS32 applications have migrated to TS35 × 15. TS32 still appears in legacy equipment retrofits, however, particularly in Germany, Austria, and Eastern Europe. A C-section variant (C20, C30, C40, C50 — named by height in mm) also exists, primarily in markets influenced by Australian standard AS 2756-1997.

For new designs, TS35 × 15 is the recommended replacement for TS32 in nearly all cases.

DIN Rail Size Comparison at a Glance

If you need a single reference to confirm a DIN rail dimension, this is it.

Inch equivalents (for markets where imperial units are specified):

• 35 mm = 1.378″
• 15 mm = 0.591″
• 7.5 mm = 0.295″
• 5.5 mm = 0.217″
• 32 mm = 1.260″

Standard mounting hole pattern (perforated rail): 6.2 mm × 15 mm oblong slots on 25 mm center-to-center spacing.

Standard supply lengths: 1 meter and 2 meters. Custom lengths available from most manufacturers and distributors.

Note: IEC 60715 also defines a TH 75-25 profile (75 mm wide × 25 mm high), but this variant sees almost no commercial use and is excluded from the comparison above.

Save or screenshot this table. It covers every standard DIN rail size you’re likely to encounter in the field.

How to Choose the Right DIN Rail Size

Knowing the dimensions is step one. Helping your customers match the right profile to their application is step two — and the same knowledge lets you stock the sizes that actually move. Three factors drive the decision: what’s being mounted, where the panel lives, and what standards the target market requires.

By Load Weight and Application Type

The single most common mistake in DIN rail selection — whether your customer is building the panel or you’re stocking inventory for resale — is underestimating the cumulative weight of mounted components.

Quick selection guide:

As a practical reference: TS35 × 7.5 on supports spaced 300 mm apart handles roughly 8–15 kg per meter of evenly distributed load under static conditions. In vibrating environments, derate by 50%. The same span in TS35 × 15 triples the safe load.

End stops (end clamps) are not optional for heavy installations. A standard end clamp provides at least 20N of lateral retention force, preventing components from walking along the rail under vibration.

By Material and Environment Conditions

The right size in the wrong material fails just as surely as the wrong size.

The critical difference between 304 and 316 stainless: 316 contains 2–3% molybdenum, which provides roughly 3–5 times the chloride pitting resistance of 304. If your panel is within 5 km of a coastline, or in any facility using chemical cleaning agents, 316 is the safer choice.

Zinc-plated steel remains the default for the vast majority of indoor industrial applications. Standard zinc coating thickness is a minimum of 6 microns (per DIN 50960, coating grade gal Zn 8c).

By Compliance Standards and Regional Requirements

This is the dimension most guides skip. It is also the one that causes the most expensive surprises in export projects.

DIN rail itself does not carry a CE mark. It is a component, not a finished device. But using non-standard rail can cause your entire panel assembly to fail certification in the target market.

Market-by-market standards reference:

A practical tip for export projects: specify “IEC 60715 compliant” on your bill of materials. It is the most widely accepted reference globally. For North American panels, confirm that the rail carries a UL Recognized Component mark. This is separate from IEC compliance and is checked during UL 508A panel inspections.

Sourcing DIN Rail: What to Look for When Buying

Once you’ve nailed down the size, material, and compliance requirements, the procurement step has its own checklist. These five points will save you from the most common sourcing pitfalls.

1. Demand IEC 60715 compliance documentation. Any reputable supplier should provide a material certificate and dimensional conformance report on request. If they can’t produce one, walk away. Dimensional deviations as small as 0.5 mm on the flange lip can prevent components from seating correctly.

2. Clarify perforation requirements upfront. Perforated rail (with pre-punched mounting slots) is the default for most applications. If you need unperforated rail — for example, when you plan to drill custom mounting holes — specify this before ordering. Confirm hole dimensions (6.2 × 15 mm is standard) and center-to-center spacing (25 mm).

3. Verify material and coating specifications. Don’t accept “steel” as a material description. Request the specific grade (DC01 per EN 10130 is standard for cold-rolled steel), the zinc coating thickness (minimum 6 µm), and the passivation treatment. For stainless steel orders, the mill certificate should state the exact grade: 1.4301 for 304, 1.4401/1.4404 for 316.

4. Confirm supply lengths and minimum order quantities. Standard lengths are 1 m and 2 m. If your design requires non-standard lengths, confirm whether cutting is included or charged separately. Typical minimum order quantities for industrial DIN rail range from 100 to 500 meters, depending on the supplier and specification.

5. Check packaging and transportation protection. DIN rail is long, thin, and easily bent during shipping. Confirm that the supplier uses rigid packaging — ideally wooden crates or reinforced cardboard tubes for lengths over 1 m. A bent rail that looks fine to the naked eye can cause mounting failures once components are loaded.

Here’s the reality of industrial distribution: DIN rail itself is a low-margin item. But the time cost of sourcing rail from one supplier, terminal blocks from another, relays from a third, and power supplies from a fourth eats into your margin fast. The distributors who win are the ones who consolidate — one supplier relationship that covers the rail and everything that mounts on it. Your customers get one shipment, one invoice, and you get one supplier to manage instead of four.

For distributors evaluating supply partners, OMCH maintains a catalog spanning 30+ product categories and over 3,000 SKUs — covering DIN-rail compatible components from power supplies and MCBs to relays and terminals. That means fewer supplier relationships to manage and more margin left in your deals. Explore the full range at www.omch.com.