The purpose of this project was to associate the output unit of the Minimitter Actiheart monitor accelerometer to the unit of acceleration (m/s²). The Actiheart monitor accelerometer was used to measure acceleration at the chest for toddlers (N = 19, 9 girls, 10 boys; M age = 2.59 years, SD = ±0.46) participating in a 30-min mastery motivation physical play program (MMPP) session. Additionally, chest location acceleration was measured for college age instructors (N = 8, 6 girls, 2 boys) leading 20 sessions over a 12-week MMPP. The toddlers were active at a level of 51 counts during the MMPP session, whereas the teachers were active at a level of 34 counts over the course of the 12-week program. To provide context for these results, data were plotted on the line of best fit established by shake-testing three Minimitter accelerometers. A range of accelerations and frequencies were produced by an electromagnetic (Emag-2000) 6-df motion simulation platform. Linear regression analysis between the input accelerations and accelerometer output was significant (p < .01, R = .998) for both the toddlers and teachers. During the MMPP, the toddlers’ activity was equivalent to 3.1 m/s² and the instructors’ was equal to 1.9 m/s². It is recommended that future research using accelerometers to classify physical activity should report data in meters per second squared to aid in direct comparison between samples and studies.