Is it the building size or stand size used for home office calculation?

I have a home office and I want to know in terms of the calculation for the percentage of the home being for the office is it the entire stand size of the property or just the building size?

It would be the office size as a percentage of the size of the property that you are paying the expenses on. So for example if your bond is only on the building then that would be the apportionment.