content: Your router should have an option to track your data usage on a monthly basis. If it isn't already enabled, you can enable it through the administrator panel, but they usually hide it in the advanced settings. If you have a Netgear router, you can go to the Advanced tab, then "Advanced Setup", and then "Traffic Meter" and check "Enable Traffic Meter", which will log to a table at the bottom of the page your usage statistics for the current day, previous day, week to date, month to date, and previous month. As an added advantage over the suggestion /u/FuckBitchesGetMaga made is that your router will track across any and all devices connecting to the internet through it, whereas a freeware tool on Windows will only be able to track usage for that single device.