The crystallinity of stretched crystallizable rubbers is classically evaluated using X-ray diffraction (XRD). Recently, a measurement technique based on quantitative surface calorimetry from infrared thermography (IRT) has been proposed in Le Cam (2018), but results obtained were not compared with XRD measurements. In the present paper, the two measurement techniques are used for evaluating of the strain-induced crystallinity of the same unfilled natural rubber. This study provides the first comparison between the two techniques. Results obtained highlight a very satisfactory agreement between the two measurements, which validates a new and simple way for evaluating the strain-induced crystallinity from temperature measurements.