Hydraulic hose size is measured by the inside diameter or ID of the hose. This is usually expressed as a "Dash Number". For all hoses except SAE100R5 hose, the Dash Number of a hose is simply the hose ID expressed in sixteenths of an inch (see the chart below for identifying 100R5 hose). A hose with a 1/2" ID for example, would be called "Dash 8" or simply "-8".
The Dash Number can usually be found on the layline of the hose, or it can be determined by actually measuring the ID of the hose. Before you cut a hose to measure the ID, be sure to measure the hose length and any offset angles first (see step 3). The chart below will help you determine the dash number of your hose.
