If your phone often doubles as your TV and you've developed a bit of a Netflix habit, then you've got to be careful about when and where you watch Netflix. Netflix doesn't let you download shows to take with you so when you are watching, you are streaming. And that can run up data charges quickly if you are watching when you're away from Wi-Fi.

To help you manage your Netflix habit and your monthly data plan, Netflix today introduced cellular data controls with its latest update to its Android and iOS apps.

To find the new controls, tap App Settings from the menu. You then need to tap the toggle switch to turn off Set Automatically before you can choose your own video-quality setting. There are five from which to choose.

Screenshot by Matt Elliott/CNET

Choose Off (Wi-Fi only) to stop all streaming when you're without Wi-Fi, or go to the other extreme and select Unlimited if you have an unlimited plan or don't care about going over your monthly data allowance. In between, there are Low, Medium and High settings.

According to Netflix's calculations, Low lets you watch 4 hours per GB of data, Medium lets you watch 2 hours per GB, and High lets you watch 1 hour per GB. If you choose the Set Automatically option, you'll be between the Low and Medium settings. Netflix states "the default setting will enable you to stream about 3 hours of TV shows and movies per gigabyte of data. In terms of bit rates, that currently amounts to about 600 Kilobits per second."

For more, watch "5 tips every Netflix user should know."