This study attempts to confirm if microwave radar sensors can be used for noncontact monitoring of relative changes in blood pressure. The efficiency of the estimation equation was then verified using data gathered using a noncontact approach while causing fluctuations in blood pressure. First, an equation to estimate blood pressure was developed. Because measurements using microwave radar sensors can measure minute scale motion on the skin surface caused by the pulsation of blood vessels, we thought that the Bramwell-Hill equation, which contains some parameters that directly indicate changes in blood pressure, would be an appropriate reference to construct an estimation equation for the noncontact method. We evaluated a straightforward equation using the pulse transit time (PTT), signal amplitude, and body dimensions as factors to determine relative changes in blood pressure. A cycling task on an ergometer, which causes blood pressure fluctuations due to changes in cardiac output, and a task involving the Valsalva manoeuvre, which causes blood pressure fluctuations due to changes in vascular resistance, were both used to test the accuracy of the equation for estimating changes in blood pressure. The two trials' findings indicated that the proposed equation, which uses microwave radar sensors to measure relative changes in blood pressure, can do so with accuracy. Particularly encouraging outcomes were attained for the variations in blood pressure brought on the variations in heart volume. Although there are still numerous problems, it is possible that this approach may lessen the load placed on patients while advancing the continuous examination of heart function.