What should be subtracted from the total length when calculating carpet needed for a doorway?

When calculating the amount of carpet needed for a space that includes a doorway, it is important to consider the physical dimensions that will affect how much carpet is actually necessary. The width of the doorway should be subtracted from the total length because the carpet will not be installed in that area. This is crucial for accurate measurements, as neglecting to account for the doorway can lead to either overestimating the carpet required or ending up with too little to complete the job. By subtracting the width of the doorway from the total length, you ensure that you are only accounting for the areas that will actually be covered by carpet, thus optimizing the flooring material and resources.