If you have a broadband internet service with a monthly download limit, you may find SurplusMeter comes in handy. It measures the download and upload traffic on your Internet connection and keeps a record of your traffic volume. It gives you all kinds of useful output statistics, like daily allowance, average daily usage, accumulated surplus, and more.
Statistics are presented in three ways: simple bytes in/out; summaries of megabytes used and remaining, and graphic meters which display at a glance when you’re getting close to exceeding your limit.
To be honest, I used this program because I was just curious at how much bandwidth I use in an average day.
Privacy Note: SurplusMeter measures only the volume of traffic on your connection. It does not look at the content of data in/out or record where it comes from. Also, SurplusMeter is completely passive; it does not send any information to anyone.