if your blood pressure is 120/80 or 140/90 mmHg its normal, if its 140/90 mmHg or higher you have high blood pressure and if its 180/110 mmHg or higher than that you have really high blood pressure.
If you think you have high blood pressure, you should visit a doctor, but some supermarkets and pharmacies have a machine you can use to give you a general idea of your blood pressure. If you use...
According to the National Heart, Lung and Blood Institute, blood pressure is considered to be "high" over 140/90 (unless you have diabetes, which it then should be no higher than 130/80)...
Blood pressure at or above 140/90 is considered high blood pressure. Conversely, pressures below 100/60 (or in some cases, 90/60) are considered low blood pressure.