Determining the roof square footage of a house to be built of re-furnished is important when deciding on the quantity of material to purchase to be used in roofing. There are different methods available to calculate roof area. The simplest is the roof square calculator which requires feeding of various roof measurement and the calculator provides with an answer. If, however, the method employed is manual, the following steps are followed to determine roof area.

- Sketch your roof on a paper sheet and label all its sections. It is on this paper where you will record the measurement of the sections to enable easy computation.
- Calculate the area of rectangular sections. This involves manual determination of length and width using a tape measure. Whether the section is a rectangle or a square, simply multiply the length and the width. This is the area and should be indicated on the paper sheet.
- Calculate the area of the triangular sections by multiplying the length(base) and the width(height) and dividing this product by two. The result is the area and should be written as the area of these sections.

(Measurement should be taken in feet to quicken the calculation of areas). - Add all areas calculated. The sum is the total square feet of the roof.

If this area was required to determine the quantity of roofing materials required, it should be converted from square feet to square. This involves dividing the square feet by a hundred and the quotient is the roof square.

It is not always necessary to climb up the roof to calculate the roof area. The following procedure may be employed to comfortably determine the area from the ground.

- Determine the measurements of the house sides using a tape measure. Add small estimates to these measurements to cater for the overhangs.
- Calculate the areas(in square feet) of all sections and sum them up to derive the square feet of the entire house.
- Convert the area so derived to squares by dividing it by a hundred.
- Determine the pitch (steepness) of a roof. This is it’s rise over it’s run. Choose a multiplier from the Roof Pitch Slope Multiplier Chart using the pitch determined.
- Multiply the house area with the multiplier to get the roof square.

The area of a roof may also be determined by use of satellites to measure roofs dimensions.