Privious studies have used an exercise stress testing blood pressure (BP) monitor to detect the double product break point (DPBP). However, not all clinical sites of physical therapy are equipped with an exercise stress testing BP monitor. Digital automatic blood pressure monitors (portable sphygmomanometer), which come in more compact, portable models, are becoming more common at general clinical sites. The purpose of this study was to investigate whether a portable sphygmomanometer can be used to derive the DPBP in healthy adults. Exercise stress tests were conducted on 11 healthy adults (8 male, 3 female), using a portable sphygmomanometer and ergometer. To investigate the double product (DP) reproducibility in derivation of DPBP by the portable sphygmomanometer, we repeated the exercise trials within one week. Moreover, using an exercise testing BP monitor, the exercise stress protocol was conducted again within 3 weeks under the same conditions. The results show that DP at DPBP calculated from measurements with a portable sphygmomanometer in the first and second exercise trials with the portable sphygmomanometer were 17084.9 ± 1109.4 and 17131.1 ± 979.2 mmHg × bpm, with an intraclass correlation coefficient of 0.84. The DP at DPBP calculated using measurements from an exercise stress testing BP monitor was 17533.9 ± 1459.2 mmHg × bpm, and the correlation coefficient with the DP value of the second trials with the portable sphygmomanometer was r = 0.80. The results of this study suggest that a comparatively accurate DPBP can be derived using a portable sphygmomanometer.