Methods, systems, and non-transitory computer-readable recording media for monitoring blood pressure are provided. The method includes calculating an estimate of deviations between every two pulse transit time (PTT) values measured at an interval of a first period, and estimating a PTT value to be measured the first period after a current time. The method also includes calculating an estimate of deviations between every two oxygen saturation values measured at an interval of a second period, and estimating an oxygen saturation value to be measured the second period after the current time. The method additionally includes calculating current systolic blood pressure and diastolic blood pressure based on an electrocardiogram (ECG) value measured at the current time, the estimated PTT value, and the estimated oxygen saturation value.
