Nominal Length (NL) for Drawer Runners — Definition & Accurate Measurement

December 2, 2025

The nominal length (NL) for drawer runners refers to the exact installation dimension of the runner when fully closed and generally corresponds to the external depth of the drawer box. It is specified in millimetres and serves as the crucial benchmark for planning cabinet carcasses and drawer systems.

What Exactly Is the Nominal Length (NL)?

The nominal length is the foundation of any drawer runner system — it defines the space required inside the piece of furniture, regardless of how far the drawer travels when opened. When joiners or fitters design a drawer system, the nominal length is the primary reference value. It always refers to the runner in its fully retracted, closed state.

Important for installation: the nominal length is not identical to the required cabinet depth. The internal clear depth (the usable interior dimension of the cabinet carcass) must always be slightly larger than the nominal length of the runner. In practice, an allowance of 3 mm to 5 mm is typically added to accommodate manufacturing tolerances and the back panel.

How to Measure and Calculate Nominal Length Correctly

To determine the correct runner for a project or to source a suitable replacement, the nominal length must be measured accurately.

Measure the existing runner: Measure the closed runner from the front edge to the rear end.
Measure the drawer box: On intact drawers, the nominal length corresponds to the external side length of the drawer (from the inside face of the front panel to the outside face of the rear panel).
Measure the cabinet carcass: Measure the internal clear depth from the front edge of the cabinet side to the inner surface of the back panel. Deduct 5 mm from this measurement. The result is the maximum possible nominal length.

Standard Dimensions and Specifications

In European furniture construction, the length increments of runner systems are based on System 32. Runners are available in standardised increments, typically in steps of 50 mm.

Compact designs start with drawer runners 250 mm, which are predominantly fitted in bathroom furniture or slim desk pedestals. For standard kitchen base units and chests of drawers, the standard dimension is usually drawer runners 500 mm. For exceptionally deep structures, such as shopfitting displays or under-stair storage, runners up to drawer runners 800 mm are used.

Nominal Length Based on Extension Type

The nominal length also dictates the usable extension stroke. A distinction must be made between the various mechanical designs:

Full extension: With full extension drawer runners, the extension stroke is identical to the nominal length. The drawer can be pulled out of the cabinet carcass by 100%.
Partial extension: A partial extension runner, frequently found in classic roller drawer runners, releases only around 75% to 80% of the nominal length due to its design. The rear portion of the drawer remains inside the cabinet.
Heavy-duty extension: With heavy-duty drawer runners, the nominal length is directly linked to the static load capacity. The specified load rating (e.g. 45 kg or 80 kg) applies to the fully extended nominal length under a uniformly distributed load.

Impact of Soft-Close and Opening Mechanisms

Additional convenience mechanisms do not alter the nominal length of the runner, but they do require consideration when calculating the internal clear depth of the cabinet.

Soft-close drawer runners brake the drawer over the final few millimetres and pull it shut gently. The mechanism is integrated directly into the runner and requires no additional space.

The situation is different for push-to-open (tip-on) systems. Push to open drawer runners require a minimal trigger stroke. To open, the drawer must be pressed inward by approx. 2 mm to 3 mm. The internal clear depth must strictly accommodate this clearance, otherwise the mechanism will jam, even if the nominal length fits into the cabinet mathematically.