I've done that and found that it varies from 6 to 8 fluid oz (in the USA) depending upon the manufacturer.

Personally, my preference is that my "cuppa" of strong coffee be in the range of 12 - 16 oz (approximately .33 to .5 liter if I remember the conversions correctly)

I don't know how this discussion got off on the "tube steak" tangent (noise)....