Estimation of crack length is one of the critical aspects of a fatigue crack growth rate testing. Several experimental techniques, such as, visual observation, compliance methods, potential difference techniques, post-failure fractography are used for crack length estimation. In this work, an attempt has been made to correlate the compliance measured from a COD gage with the compliance measured from actuator displacement for a given set of grips and fixtures. Experiments have been carried out at both room temperature as well as two elevated temperatures of 300 °C and 550 °C. A systematic trend between actuator displacement range and COD displacement range was observed as a function of test temperature, which results in decreased actuator compliance. © 2017 ICF 2017 - 14th International Conference on Fracture. All rights reserved.