Objective To propose and validate a new method for estimating cardiac output based on the total arterial compliance (Ct) formula that does not need an arterial waveform and to apply it to brachial oscillometric blood pressure measurements (OBPMs). Methods One hundred subjects with normal heart anatomy and function were included. Reference values for cardiac output were measured with echocardiography, and Ct was calculated with a two-element Windkessel model. Then, a statistical model of arterial compliance (Ce) was used to estimate cardiac output. Finally, the measured and estimated cardiac output values were compared for accuracy and reproducibility. Results The model was derived from the data of 70 subjects and prospectively tested with the data from the remaining 30 individuals. The mean age of the whole group was 43.4 ± 12.8 years, with 46% women. The average blood pressure (BP) was 107.1/65.0 ± 15.0/9.6 mmHg and the average heart rate was 67.7 ± 11.4 beats/min. The average Ct was 1.39 ± 0.27 mL/mmHg and the average cardiac output was 5.5 ± 1.0 L/min. The mean difference in the cardiac output estimated by the proposed methodology vs. that measured by Doppler echocardiography was 0.022 L/min with an SD of 0.626 L/min. The intraclass correlation coefficient was 0.93, and the percentage error was 19%. Conclusion Cardiac output could be reliably and noninvasively obtained with brachial OBPMs through a novel method for estimating Ct without the need for an arterial waveform. The new method could identify hemodynamic factors that explain BP values in an ambulatory care setting.