Predicting thermal strain and providing a visual representation of the predicted thermal strain on a subject. A computerized model combines subject data, fabric data, and environmental conditions to simulate the thermal comfort of the subject wearing a plurality of fabric layers over time. The visual representation indicates the simulated thermal comfort on an image of the subject with the plurality of fabric layers. A user interface enables a user to modify or define the input data to compare the predicted thermal comfort of the subject wearing different garments under the same working conditions.