Interfaces with good usability help their users complete more tasks in less time and with less effort, which gives them greater satisfaction. Given the vast array of options available to users today, usability is an important interface feature that may lead to the commercial success or failure of a software system. Despite its importance, few educational tools are available to help usability teachers and students. Knowing how to measure interface usability is one of the basic concepts that students should learn when they study the theme. This paper presents UsabilityZero, a web application to support the teaching of usability concepts to undergraduate students. By using UsabilityZero, students interact with a system displaying a reduced usability interface and, later, with the same system exhibiting an increased usability interface. Considering the use of UsabilityZero by 64 students, the differences between the interface with reduced and increased usability were: (i) 61.5% decrease in the number of clicks; (ii) 62.2% decrease in the time to perform tasks; (iii) 92.9% effectiveness increase; and (iv) a 277.3% satisfaction increase. During their experience with UsabilityZero, students learn how to measure efficiency, effectiveness, and satisfaction of user interfaces. After using the application, Information Systems and Computer Science students who had never been in touch with the subject could identify key usability aspects. The students’ perception of efficiency, effectiveness, and satisfaction as usability measures was higher than 80%. Also, they could identify some usability criteria and understand how measurements change when some of them are present in the interface design. As a result, over 92% of these students said they recognized the importance of usability to the quality of a software product, and 79% declared that their experience with the application would contribute to their professional lives.