Smartphone use in learning environments can be productive or distracting depending upon the type of use. The use is also impacted by the learner's view and understanding of the smartphone and self-regulated learning skills. Measures are needed to specify uses and learner understandings to address the implications for teaching and learning. This study reports on the development of a multi-factor inventory designed to measure multitasking while studying, avoiding distractions while studying, mindful phone use, and phone knowledge. The inventory was completed by 514 undergraduate students enrolled in a first-year seminar. The results indicate good reliability and a three-factor structure with multitasking and avoiding distraction merging into one factor. The resulting measure can support research to improve self-regulation of smartphone use. Suggestions regarding instructional use are provided.