Dating to Colonel John Paul Stapp MD in 1975, scientists have desired to measure live human head impacts with accuracy and precision. But no instrument exists to accurately and precisely quantify single head impact events. Our goal is to develop a practical single event head impact dosimeter known as “Intelligent Mouthguard” and quantify its performance on the benchtop, in vitro and in vivo.In the Intelligent Mouthguard hardware, limited gyroscope bandwidth requires an algorithm-based correction as a function of impact duration. After we apply gyroscope correction algorithm, Intelligent Mouthguard results at time of CG linear acceleration peak correlate to the Reference Hybrid III within our tested range of pulse durations and impact acceleration profiles in American football and Boxing in vitro tests: American football, IMG=1.00REF-1.1g, R2=0.99; maximum time of peak XYZ component imprecision 3.6g and 370rad/s2; maximum time of peak azimuth and elevation imprecision 4.8° and 2.9°; maximum average XYZ component temporal imprecision 3.3g and 390rad/s2. Boxing, IMG=1.00REF-0.9g, R2=0.99, R2=0.98; maximum time of peak XYZ component imprecision 3.9g and 390rad/s2, maximum time of peak azimuth and elevation imprecision 2.9° and 2.1°; average XYZ component temporal imprecision 4.0g and 440rad/s2. In vivo Intelligent Mouthguard true positive head impacts from American football players and amateur boxers have temporal characteristics (first harmonic frequency from 35Hz to 79Hz) within our tested benchtop (first harmonic frequency <180Hz) and in vitro (first harmonic frequency <100Hz) ranges.Our conclusions apply only to situations where the rigid body assumption is valid, sensor-skull coupling is maintained and the ranges of tested parameters and harmonics fall within the boundaries of harmonics validated in vitro. For these situations, Intelligent Mouthguard qualifies as a single event dosimeter in American football and Boxing.