Calculating rental vs personal use of home

[dheyrend]

I rent out part of my home.  I use 1 room, and I rent out 3 rooms plus a basement apartment with a shared entrance (hallway).  Rooms 1-4 share the upstairs living area.

My room (Room 1) is 110 sf

Room 2 is 110 sf

Room 3 is 110 sf

Room 4 is 244 sf

basement room is 672

Shared living space for 4 upstairs bedrooms is 1132 sf

Total: 2368

What percentage is personal vs rental?  I've heard different advice of how to calculate the percentage.

[AnnetteB6]

Generally, using the square feet of the rented space versus the total home is an accepted method of determining the personal versus rental percent.  Since you use the shared space personally as well as using it for rental purposes, you could choose to leave that portion out of the rental calculation to be conservative in the total rental space.

Leaving out the shared space, your calculation would be 110 + 110 + 244 + 672 / 2368

No matter how you decide to do the calculation, be sure to keep some notes with your tax return to explain how it was done.