Product appearance plays a significant role in generating appeal for consumers and subsequent commercial success for mass-market products. Associated with the design and manufacture of many mass-market products is significant financial investment and thus also significant risk. This risk is particularly severe for established or mature markets such as consumer electronics and vehicles where designs must retain a brand identity and differentiate from other products while still being easily identifiable, and avoid potential design right or trade dress infringement. Within the design process there is ‘styling’, the activity primarily concerned with the creation of products’ form and appearance. While appearance is the primary concern in styling there is a wide range of factors that must be considered alongside appearance when designers evaluate potential design concepts. While there exists many tools and methods to objectively evaluate and communicate factors such as cost, performance, manufacture or ergonomics, there are few strategies to assist designers in objectively evaluating and reasoning on appearance, despite its relative importance to the market success of products. The aim of this thesis is to improve the styling process by researching and creating a method to more objectively measure and compare product appearance. In proposing a method and achieving the aim three major areas of research are addressed. The first is to create an approach to visually decompose products into constituent features to explore their influence on overall appearance. The second is to create a method of measurement to analyse the geometry of features and enable comparison across product ranges. The third is to investigate how the measures can be applied to assist designers during the styling process and provide insights into the strategic use of visual branding. The progression through these research areas and the subsequent proposed method form the key contribution to knowledge of this thesis. Through the application of the method to various case studies and a comprehensive study in its complete form, the method is validated and its potential use to designers demonstrated.