Now that Comcast has decided to start imposing monthly caps on its Internet users, there are a lot of Mac users that are taking a real interest in monitoring just how much bandwidth they are using. There are some options for helping keep track of your Mac’s Internet usage, and considering they are free, they won’t break your bank.
MenuMeters MenuMeters from Raging Menace lets users view their network data activity in real time in their menu bar. It includes graphs, throughput information for the data coming into and going out from your Mac, and cumulative data throughput totals. It also includes information about other system activities including disk, CPU, and memory usage. 
MenuMeters
MenuMeters is free and available for download at the Raging Menace Web site.
iStat menus Like MenuMeters, iStat menus serves up data about your network activity including current and total bandwidth usage in your menu bar. It also tracks other system-related information like disk usage, CPU and memory usage, computer temperatures, and fans and power. As a bonus, it includes a handy date and time menu bar item that shows the current time, a calendar, and multiple time zones. 
iStat menus
iStat menus is free and available for download at the iSlayer Web site.
SurplusMeter SkoobySoft’s SurplusMeter is a stand-alone application that compares the amount of bandwidth you are using to the cap level that you specify. For example, Comcast’s monthly data limit is 250GB, so you can set SurplusMeter’s Download limit field to 250. It shows how close you are coming to your monthly cap with thermometer displays, and lets you specify whether or not uploaded data should count against your bandwidth cap.
SurplusMeter is free and available for download at the SkoobySoft Web site, but it is not Universal Binary, so Intel-based Macs will run the app in the Rosetta emulation environment — potentially slowing down your computer. 
SurplusMeter
While all of these applications are useful, they share a common downfall. They track all network activity instead of just Internet-related activity, and they track the data going in and out of a single Mac, which means each computer on the network will have to be monitored individually. Also, if you switch to a different network, these utilities will track that activity as if you never left the original network.
The best solution for networks with multiple computers and networks with computers that come and go is a monitoring system that tracks all of the data coming into and going out of your broadband modem. For users where that isn’t an option, however, one of these applications might be just the ticket. Jeff Gamet is TMO’s Managing Editor and Reviews Editor. He lectures, teaches and speaks on Mac OS X and design-related topics, and is the author of The Designer’s Guide to Mac OS X from Peachpit Press.