Described herein are systems and methods for calculating respiratory parameters based on thermal measurements. In one embodiment, a system includes an inward-facing head-mounted thermal camera (CAM) and a computer. CAM takes thermal measurements of a region below the nostrils (THROI) of a user, and THROI are indicative of the exhale stream. Optionally, CAM is located above the user's upper lip and less than 15 cm from the user's face, and CAM does not occlude any of the user's mouth and nostrils. The computer generates feature values based on THROI and utilizes a model to calculate a respiratory parameter based on the feature values. The model was trained based on previous THROI of the user taken during different days. Optionally, the respiratory parameter is indicative of the user's breathing rate. Optionally, the computer detects whether the user breathed primarily through the mouth or through the nose.
