To calculate the home office deduction, you would use the following methodology:
Your home office business deductions are based on either the percentage of your home used for the business or a simplified square footage calculation.
The most exact way to calculate the business percentage of your house is to measure the square footage devoted to your home office as a percentage of the total area of your home. If the office measures 150 square feet, for example, and the total area of the house is 1,200 square feet, your business percentage would be 12.5%.
An easier calculation is acceptable if the rooms in your home are all about the same size. In that case, you can figure out the business percentage by dividing the number of rooms used in your business by the total number of rooms in the house.
