How do I calculate my home office and total percentage including land storage

I have a home office in my home. We also have material and equipment stored on our property and a seperate structure for storage.  How do I calculate the total sq. footage of the house to include the land storage.  House is 3000sf, office is 300sf, building is 200sf, land storage area is 2000sf and total property we live on is 2 acres.

If I say office plus building plus land I have 2500sf.  House is 3000sf plus building and land I'm at 44% usage. But should I actually calculate the sq ft. as total 2 acres to get accurate percentage of use?  I hope this makes sense.

Thank you!