This paper outlines a formal description for the distribution by value curve (DBV), which is widely employed to represent size distributions of multi-item inventories. It gives a convenient mathematical expression for the often used lognormal DBV curve and reveals its symmetrical nature when represented on a unit square. A Pareto DBV curve that has been used in the literature is detailed and shown to be skewed to one direction. Two alternative forms for the DBV curve are suggested: symmetric-Pareto and power, which may be more suited to mathematical manipulation. The latter can also represent a wider class of inventories.