There are a few options you can use to monitor bandwidth utilization on your device(s). Depending on your router as well, this may have the capacity to monitor the traffic used per device over a period.
On Windows, NetBalancer is a freemium application that can allow you to monitor traffic on your Windows device, and set some basic QoS rules:
Another free solution is also NetWorx, with the same functionality. However as stated, if you're using an Android phone for tethering, there are data limits you can apply which might help (even if you need to monitor them hourly).
For Mac, use the inbuilt Activity Monitor for network.