Dimension converter.

One inch equals 25.4 millimeters exactly, by international agreement since 1959. The relationship is fixed: 1 in = 25.4 mm = 2.54 cm = 0.0254 m. There is no rounding in the definition itself.

28 millimeters is 1.10 inches. That measurement is worth memorizing because 28mm is the most common neck finish diameter for personal care and household products. A 28-400 closure has a 28mm thread diameter; its imperial equivalent is just over 1 inch.

Because the actual conversion is 2.54 cm per inch, not 2.50. That four-hundredths difference compounds quickly. A 10-inch label height is 25.4 cm, not 25 cm. The gap can cause misalignment at print, so use the precise figure when specifying packaging artwork.

Millimeters, almost universally, for neck finishes and bottle heights. When a spec sheet lists centimeters, it typically covers macro measurements such as carton size rather than bottle tolerances. Always confirm the unit in writing before approving tooling.

38mm converts to 1.50 inches. It is the standard neck finish size for wide-mouth jars, pump dispensers, and larger lotion bottles. The 38-400 finish is one of the most common in personal care packaging.

Multiply by 100. One meter is exactly 100 centimeters. In packaging work, meters appear most often in shipping and pallet dimensions. Bottle heights and neck finishes are specified in millimeters or centimeters, rarely in meters.