The relationship between the heart's electrical and mechanical activities is expressed by Mechano-Electric Coupling (MEC) term, and blood pressure (BP) is the output of these activities. Electrocardiogram (ECG) is a representation of heart's electrical activity. Previous studies show that there is a nonlinear relationship between the ECG signal and BP values. This paper presents a new algorithm for estimating BP using only the ECG signal and without any cuff. A new feature vector extraction method in the frequency domain, called the frequency whole-based method, is proposed. According to the British Hypertension Society (BHS) standards, the proposed algorithm achieves grade B for the Diastolic Blood Pressure (DBP) and grade C for Mean Atrial Blood Pressure (MAP) estimations on MIMIC II dataset.