There is no clear boundary between normal blood pressure and hypertension, and the criteria for hypertension are defined on the basis of clinical and epidemiologic data. Hypertension is categorized into grades 1-3 based on the level of elevation of blood pressure.Grade 1 hypertension, also called mild hypertension, is a systolic blood pressure of 140 mmHg-159 mmHg and/or a diastolic blood pressure of 90 mmHg-99 mmHg.Grade 2 hypertension, also called moderate hypertension, is a systolic blood pressure of 160-179 mmHg and/or a diastolic blood pressure of 100 mmHg to 109 mmHg. grade 3 hypertension, also called severe hypertension, is a systolic blood pressure ≥180 mmHg and/or a diastolic blood pressure ≥110 mmHg. when systolic and diastolic blood pressures fall into different grades, the higher grade is used as the standard. The grading and classification of hypertension helps in treatment and predicting prognosis.