SurplusMeter is a handy application for Mac developed by SkoobySoft and is used for calculations regarding amount of downloaded and uploaded data.
It was basically designed to help users that have a monthly limit on downloaded/uploaded data, but it can be easily used by anyone. The main interface is simple and grants the Mac users quick access to all of the tools and settings. This piece of software can be set up to measure the amount of data transferred, based on the user's connection (PPP modem, Ethernet port, Airport, Network Card, Adaptor). Also, in order to get an accurate result, the users must set up the day of the month in which the transfer begins to be monitored, as well as the maximum limit of the download. After the limit is provided, the tool automatically calculates how much traffic you have left for the current month, as well as the number of the remaining days. At any time, one can reset the amount of data transferred, in order to begin another month or choose another connection mode. The customization of the tool is poor to non-existent, as the preferences menu only allows the users to modify the separator used in bytes numbers.
All taken into consideration, it is safe to say that SurplusMeter is a handy tool for measuring the amount of data transferred through a Mac (per month).