Purpose <p>To quantify a helmet-to-head pressure threshold for comfort and a preferred range of chin strap tightness in American football athletes.</p> Methods <p>A football helmet model was instrumented with capacitive force sensors and load cells to measure contact pressure and chin strap tension. Anthropometric measurements and 3D head scans were obtained to analyze head shape and hair volume. Twenty-eight collegiate football athletes participated in the study. Participants adjusted the helmet at repeatable tightness increments until the helmet was too tight and/or uncomfortable and provided subjective ratings of fit in each cranial region (frontal, temporal, parietal, occipital), and an overall comfort rating at each tightness increment. Helmet-to-head contact pressure and chin strap tension were recorded at each tightness increment.</p> Results <p>Head shape dimensions were associated with contact pressure, while hair volume was not. Helmet-to-head pressure was associated with comfort. Participants’ subjective feedback indicated that average pressure in the range of 4–7&#xa0;kPa is comfortable, while most participants indicated average pressures above 7&#xa0;kPa or pressure concentrations exceeding 20&#xa0;kPa are uncomfortable. The subjective feedback also indicated average chin strap tension in the range of 5–13 N was preferred by the athletes. Given the area of the chin cup, the average pressure exerted on the chin is consistent with the helmet-to-head pressures that were reported to be comfortable.</p> Conclusions <p>Head shape features beyond circumference affect helmet comfort, suggesting more information is required to fit helmets properly than only head circumference. These findings provide objective helmet comfort and chinstrap fit thresholds for American football athletes, which can be used to validate fitting conditions on surrogate headforms in laboratory testing.</p>