An estimate of how much your printer and printer cartridge purchases will combine in costs in a year, here’s what you do. Multiply the number of pages you printer per week by 52 to get a year’s sum. Afterwards, divide that number with the cartridge page yield. The result is the number of cartridges you will need per year. Suppose you print 25 pages in a week, you would be printing 1300 pages in a year. Suppose your cartridge can print 200 copies, that means you have to buy 7 cartridges per year to print 1300 pages. To reduce ink jet cartridge purchase costs, switch from original ink cartridges to compatible ink jet cartridges.