How to Convert MM to Inches (“)

Hydraulic hose sizes are usually expressed in inches.
Common hydraulic hose sizes include 1/4 inch, 3/8 inch, 1/2 inch, 5/8 inch, 3/4 inch, 1 inch, and more.
The size of the hydraulic hose will affect its pressure, flow, and connection method. Therefore, when selecting a hydraulic hose, it is often necessary to convert millimeters into inches according to actual needs and choose the most suitable hose size.

MM to Inches
MM to Inches

1mm = (1/25.4)″ = 0.03937007874″

Millimetre (mm)Inch ( ” )Millimetre (mm)Inch ( ” )
2mm3/32″40mm1 5/8″
3mm1/8″45mm1 3/4″
4mm5/32″48mm1 7/8″
6.5mm1/4″54mm2 1/8″
7mm9/32″57mm2 1/4″
8.0mm5/16″60mm2 3/8″
9.5mm3/8″63mm2 1/2″
11mm7/16″65mm2 9/16″
13mm1/2″68mm2 11/16″
16mm5/8″70mm2 3/4″
22mm7/8″80mm3 1/8″
25mm1″83mm3 1/4″
28mm1 1/8″90mm3 1/2″
30mm1 3/16″102mm4″
32mm1 1/4″114mm4 1/2″
35mm1 3/8″127mm5″
38mm1 1/2″152mm6″

Please Note – The measurements are approximate and may not match up exactly to the inch amount.

History/origin: An inch is a unit of measurement that is equal to 1/12 of a foot, or 2.54 centimeters. It is believed to have originated from the width of a thumb, as “inch” comes from the Latin word “uncia,” meaning “one-twelfth part.” The use of inches as a unit of measurement dates back to the 7th century, when it was used in England as a standard for measuring lengths and distances. Today, it is still commonly used in the United States and the United Kingdom, particularly in industries such as construction, engineering, and manufacturing.


hydraulic hose size chart

Here is a chart of common hydraulic hose sizes and their corresponding dimensions:

  • 1/4 inch: Inner diameter 6.4 mm, Outer diameter 13.4 mm
  • 3/8 inch: Inner diameter 9.5 mm, Outer diameter 17.4 mm
  • 1/2 inch: Inner diameter 12.7 mm, Outer diameter 20.6 mm
  • 5/8 inch: Inner diameter 15.9 mm, Outer diameter 23.7 mm
  • 3/4 inch: Inner diameter 19.1 mm, Outer diameter 29.3 mm
  • 1 inch: Inner diameter 25.4 mm, Outer diameter 36.6 mm

It’s important to note that different manufacturers and models of hydraulic hoses may have slightly different dimensions. When selecting a hydraulic hose, it’s important to choose the right size based on your specific needs and refer to the relevant specification tables.