A graph, usually containing three parallel scales graduated for different variables, so that when a straight line connects values in any two, the related value may be read directly from the third at the point intersected by the line. For example, the most accurate way to decide upon the correct drug dose for a new born baby is to calculate it according to body surface area. The nomogram for this will contain a vertical line with body weight and another with length. Placing a ruler between the two values for a particular baby will cross a third line, showing surface area.