Before changing the toner, use the printer’s status print out to see how many pages printed with the current cartridge. The printer documentation should tell you how to get that report. Alternatively, if it is a network printer, you should be able to see the status page by using a Web browser. Just enter the IP address in the browser URL bar. The network router probably has an IP of 192.168.1.1. If the printer is assigned a dynamic address the printer most likely has an IP of one number higher than your computer(s). With one computer on a network, the PC often will be at 192.168.1.100. In this case, the printer likely is at 192.168.1.101. Two computers on the network? Then try 192.168.102. With a static IP address, you should already know the printer’s address.
Use the same technique to get statistics if beginning part way into the toner cycle. In this case you will have to estimate full toner use based on the claimed average pages printed (from the printer manufacturer details) and a ratio of current printouts for the known time length of printing.
There is a slight disadvantage in this case because the use to date may not represent typical use, but it is probably not significant enough to make a difference. For example, if the printer is supposed to do 5,000 pages of normal printing per toner and you’ve used it for six months. So far, 3,000 pages have printed. If the best price available for toner is $85.00 then divide 3000 by 5000. Multiple the result, 0.6 times $85.00 for a cost to date of $51.00. Start the spreadsheet with either the full cost of toner or the partial cost.