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. Divide that figure with the cartridge page yield to find out the number of cartridges you will need per year. If you print 25 pages per week, you’d print 1300 pages per year. If your cartridge can print 200 copies, you will need to buy 7 cartridges in a year to print 1300 pages. So you won’t have to keep buying expensive original cartridges, you can switch to compatible ink jet cartridges.