Where do measurements for an opening typically begin?

Measurements for an opening typically begin from the inside jamb to inside jamb because this method provides the most accurate reference for the size of the opening that will accommodate a door, window, or other architectural features. The inside jamb represents the actual space where the frame or casing will fit, ensuring that any trim or finishing work aligns perfectly with the structure.

Using this approach allows for consideration of the space needed for the installation of the item, facilitating a fit that not only looks good aesthetically but also functions properly. This method is particularly crucial in construction and remodeling, where fitting elements into existing structures requires precise measurements to ensure functionality and structural integrity.

Other measurement methods, such as measuring from the floor to the ceiling or diagonally from corner to corner, do not account for the specifics of the frame or opening itself, which can lead to inaccuracies in determining the required size for installations. Additionally, measuring from the outside of the wall may not reflect the necessary internal dimensions needed for a proper fit.