4mm

4 millimeters is a unit of length in the metric system equal to 0.004 meters. In inches, it is approximately 0.157 inches (4 divided by 25.4). This size appears in a variety of everyday and technical contexts, serving as a standard reference point for components, tools, and materials.

Common uses and contexts

In textiles and crafts, 4 mm is a common size for crochet hooks and knitting needles, and for beads and cords marketed by bead size. Jewelry makers frequently refer to 4 mm beads and spacers as a standard dimension for designing pieces. In hardware and machining, 4 mm corresponds to the diameter of many small drill bits and to the outer diameter of M4 fasteners, which are widely used in electronics and light mechanical assemblies. In electrical work and laboratory settings, 4 mm is associated with banana connectors and plug conventions that use a 4 mm terminal size for test equipment.

Related measurements

4 mm lies between smaller common sizes such as 3 mm and larger ones such as 5 mm, and it is one of several millimeter sizes used across crafts, manufacturing, and engineering. Precision instruments, calipers, and rulers commonly mark measurements in millimeters, making 4 mm a routine reading point for quick approximations and tolerances.

Overview

The 4 mm dimension serves as a versatile reference across disciplines, bridging practical craft applications with mechanical and electrical components, and illustrating how a single metric size integrates into both everyday objects and technical hardware.