Dash size chart
The dash number is the nominal inside diameter in sixteenths of an inch. That is a definition, not a lookup — which is why the arithmetic below is exact and the caveats underneath matter more than the numbers.
| Dash | Inches | Decimal in | Millimetres |
|---|---|---|---|
| -4 | 1/4″ | 0.2500 | 6.35 |
| -5 | 5/16″ | 0.3125 | 7.94 |
| -6 | 3/8″ | 0.3750 | 9.52 |
| -8 | 1/2″ | 0.5000 | 12.70 |
| -10 | 5/8″ | 0.6250 | 15.88 |
| -12 | 3/4″ | 0.7500 | 19.05 |
| -16 | 1″ | 1.0000 | 25.40 |
| -20 | 1-1/4″ | 1.2500 | 31.75 |
| -24 | 1-1/2″ | 1.5000 | 38.10 |
| -32 | 2″ | 2.0000 | 50.80 |
| -40 | 2-1/2″ | 2.5000 | 63.50 |
| -48 | 3″ | 3.0000 | 76.20 |
Two caveats
It is nominal. Actual bore varies with construction — a compact hose in a given dash size does not necessarily share the bore of a standard one in the same size. Take the real figure from the datasheet for the grade you are buying.
Fittings use the same numbers differently. On a JIC or SAE fitting the dash refers to the tube outside diameter the fitting suits, not the hose bore. A -8 hose and a -8 fitting are a matched pair by convention, not because the two dimensions are the same thing.
Choosing a grade rather than a size? Browse hydraulic hose by construction.