US tax deductions for spare room, use footage or number of rooms?

[Bruna-and-Siana0]

We have a spare room in our apartment and we often rent it in AirBnB. We live in the apartment. For 2017 deductions, we are reporting direct expenses for the room (sheets, laundry, netflix, snakcs, etc) and also apartment expenses (includes personal + rental such as utilities, insurance, etc). To calculate the deductions corresponding to the rental room, do we use the footage of the room or the number of rooms?

If we go by footage, the room it's ~20%  of our entire apartment. If we use, number of rooms, its 50% as we have 2 bedrooms (ours and the one it's in AirBnB). Which one should we use? 

[Linda108]

If you google IRS, you can find that the tax law allows either % of space or days rented to determine shared space deductions.  There is also a great article located on Air BNB Help from accounting firm Ernst and Young about deductible elements.  Look it up.