# How Do You Calculate Gross Floor Area?

Calculating the gross floor area requires you to know the area of the floors and the width of the interior walls. For the floors, you will need a tape measure and a calculator. To determine the wall width, you may need to contact the builder. The only rooms that aren't included are plazas or rooftops.

1. Measure the floor area

Measure the floor are by going through one room at a time. Measure both the length and width of each room. In the case of rooms that do not have a standard geometry, break the room up into smaller shapes and add the area. For example, consider a room that has a main section that is 10 feet wide and 10 feet long has a narrower section that is five feet wide and long. You would take the two areas, 100 ft^2 and 25 ft^2, and add them. Find the total area by adding all the room areas together at the end.

2. Determine the length of the walls

Use the tape measure and measure the length of the walls. Do this for the walls in each room.

3. Determine the width of the interior walls

Determine the width of the interior walls and multiply this with the length to determine the area. To do this, you may need to contact your builder or view schematics.

4. Add all the areas

Add all the areas up. This final number is the gross area.

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