Proper Bridge Placement. Proper Bridge Placement is achieved through the following instructions: The "f" hole notches are only a basic guide and are not an exact placement guide. The proper bridge location is calculated using the MENSUR which is a ratio of neck length to bridge location. To determine the MENSUR of a violin/viola, first measure the distance from the nut to the edge of the violin next to the neck. Take this total (which is 13 cm on most 4/4 violins), divide by two (13 cm/2=6.5 cm), and multiply by three (6.5cm x 3= 19.5cm). The resulting measurement (from the edge by the neck, to the center of the bridge foot) is the proper location of the top of the front of the bridge (side closest to the fingerboard) for violin, thus a 2:3 ratio. For the Cello the ratio is 7:10 and the Bass is 3:4.