Try keeping an eye on your Wh/mile. As stated in a post above, that is the best indicator of how much energy the car is using as you drive. Trying to relate miles driven to "miles" of range is a losing proposition -- better to think in terms of Wh/mile. The car tracks it for you, and you can chose to display the average over 5 miles, 15 miles, or 30 miles. You can also reset one of your trip gauges (B, probably) to track your energy use over a longer period, such as the winter season, and compare it to your lifetime average or to any records you have of other periods of time. I always have the energy app displayed in the right-hand third of the instrument cluster, and the average Wh/mi is displayed below the graph.
And by the way, some other EVs track their energy consumption as the miles/kWh, which makes sense. It might be easier to think in terms of miles/kWh as analogous to miles/gallon. As an example -- If you use 333 Wh/mile, then that is exactly 3 miles per kWh.A Model S should get at lest 3 on a nice day at reasonable speeds in mild weather. On a cold day, running short trips, your average energy consumption might be 400 Wh/mi, or even more. So that is only 2.5 miles per kWh. You know how big your battery is, and how much it is charged, so that can be used to give you an idea of range under various conditions. But first you need the data. (I keep a paper log, but there are also third party logging tools that run on a phone or a PC and collect data directly from your car.)