The Low Voltage conduit fill is the same as electrical pipe sizing. Lets put it into perspective a Siamese Cable (coax + Power) has an OD (Outside Diameter) of approx 11.4mm +- .2 mm this Siamese cable and Cat5e having an OD of 4.76 approx 4.76mm +- .2 mm
There is a difference between Schedule 40 and Schedule 80.
Check this chart here