Matt Kastner of Coastal Business Supplies Inc. estimates that every milliliter of ink yields about 1 square foot of printing. On a table of print yields of various HP cartridges, the number of pages ranged from 31 to about 40 per milliliter.
According to Epson, print yield can vary due to temperature, images being printed, print settings and humidity. Estimated cartridge yield is based on ISO tests, which require that the printer is in default mode and printing continuously. Infrequent printing can lower the total print yield. The manufacturer's website is the best source of estimated print yield for each cartridge.