Abstract A ThermoGravimetric Analyser with Differential Scanning Calorimeter (TGA-DSC) has been simulated to evaluate the influence of different parameters on thermal lag. Two virtual materials with selected properties were created and combined with two heating rates. A three-dimensional mesh was created based on measurements in the actual TGA-DSC. Specific models have been applied and boundary conditions have been configured, including a programmed Proportional Integral Derivative (PID) controller to regulate temperature. The results showed that a sample with a lower thermal diffusivity had greater temperature differences when compared to the furnace temperature than a sample with a higher thermal diffusivity. Biot number has also been computed to analyse temperature differences within the sample. Thermal diffusivity and Biot number effects were miniscule compared to the heating rate, which increased sample temperature instability and temperature differences within the sample.