Blood Pressure Calculator
Classify a blood pressure reading into the standard categories (normal, elevated, stage 1 or 2 hypertension, crisis), with pulse pressure and mean arterial pressure.
Cómo usar esta calculadora
- 1Enter your systolic pressure, the top (higher) number.
- 2Enter your diastolic pressure, the bottom (lower) number.
- 3Read the category, determined by whichever number is higher.
- 4See the pulse pressure and mean arterial pressure for extra context.
Cómo funciona
Blood pressure categories
Normal: below 120 and below 80 Elevated: 120–129 and below 80 Stage 1: 130–139 or 80–89 Stage 2: 140+ or 90+; Crisis: 180+ or 120+
Blood pressure is reported as two numbers: the systolic pressure, the higher figure, is the pressure in the arteries when the heart beats and pushes blood out; the diastolic pressure, the lower figure, is the pressure between beats when the heart relaxes and refills. The reading is written as systolic over diastolic, in millimetres of mercury. The 2017 American College of Cardiology and American Heart Association guidelines sort readings into categories, and the rule is that the higher of the two numbers determines the category — so a reading of 138/78 is Stage 1 hypertension because the systolic is in that range, even though the diastolic is normal. Two derived figures add context: the pulse pressure is the gap between systolic and diastolic, and the mean arterial pressure (MAP) estimates the average pressure over a full cardiac cycle, weighted toward the longer diastolic phase, giving a single number for the perfusion pressure driving blood to the organs.
Ejemplo resuelto
A reading of 118/78 is Normal, because both numbers are below their thresholds (120 and 80). Its pulse pressure is 118 − 78 = 40 mmHg, and its mean arterial pressure is 78 + (118 − 78) ÷ 3 ≈ 91.3 mmHg — comfortably in the healthy range for organ perfusion.
Blood Pressure Calculator: la guía completa
Understanding the two numbers
A blood pressure reading always comes as a pair, and each number tells a different part of the story. The top number, systolic pressure, is the peak pressure in the arteries when the heart contracts and ejects blood — the surge with each beat. The bottom number, diastolic pressure, is the lowest pressure, occurring while the heart relaxes and fills between beats. Both matter, and both are measured in millimetres of mercury, a unit inherited from the mercury column of the original blood pressure devices. A reading of 118 over 78 means a systolic of 118 and a diastolic of 78.
The rule for categorising a reading is that the higher category wins — whichever of the two numbers falls into the worse range determines the classification. This catches the important cases where only one number is elevated. Isolated systolic hypertension, where the top number is high but the bottom is normal, is common in older adults as arteries stiffen, and it carries real risk despite the normal diastolic. By always taking the higher category, the guidelines ensure that a concerning number in either position is not overlooked, which is why a reading like 145 over 85 is classed as Stage 2 on the strength of the systolic alone.
Why blood pressure matters, and the categories
High blood pressure, or hypertension, is often called a silent killer because it usually produces no symptoms while quietly damaging the body over years. Sustained high pressure strains the heart, stiffens and damages artery walls, and raises the risk of heart attack, stroke, kidney disease, and other serious conditions. Because it is symptomless, many people have it without knowing, which is why routine measurement and understanding the categories matter so much. The categories exist to flag risk early, before damage accumulates, and to guide when lifestyle changes or treatment are warranted.
The 2017 guidelines lowered the thresholds compared to older definitions, reflecting evidence that risk begins to rise even at pressures once considered acceptable. Normal is below 120 over 80. Elevated (120–129 systolic with normal diastolic) is a warning zone where lifestyle changes are advised. Stage 1 hypertension begins at 130 over 80, and Stage 2 at 140 over 90, with each stage prompting more active management. A reading at or above 180 over 120 is a hypertensive crisis requiring immediate medical attention, especially if accompanied by symptoms like chest pain, shortness of breath, or vision changes. The categories translate a pair of numbers into a clear sense of where a person stands.
One reading is not a diagnosis
The single most important thing to understand about a blood pressure reading is that one measurement, on its own, does not diagnose anything. Blood pressure is remarkably variable, rising and falling throughout the day with activity, stress, caffeine, position, and even the time of day. It commonly spikes in a clinical setting — the well-documented 'white coat effect', where anxiety about being measured pushes the reading up. A single high reading may reflect a stressful moment rather than a persistent problem, and a single normal one does not rule hypertension out.
For this reason, proper assessment relies on multiple readings taken over time, under calm and consistent conditions, and increasingly on home monitoring, which avoids the white-coat effect and captures pressure during normal daily life. Diagnosis and treatment decisions are made by a healthcare professional considering the pattern of readings alongside a person's overall risk factors, not from any single number. This calculator classifies an individual reading against the standard categories, which is useful for understanding what a number means, but it is explicitly a screening and educational aid. Anyone with consistently elevated readings, or a crisis-level reading, should consult a doctor rather than rely on a calculation.
Preguntas frecuentes
What is a normal blood pressure?
Under the 2017 ACC/AHA guidelines, normal is below 120 systolic and below 80 diastolic. 120–129 systolic (with diastolic under 80) is Elevated, 130/80 begins Stage 1 hypertension, and 140/90 begins Stage 2. The higher of the two numbers decides the category.
What do the two blood pressure numbers mean?
The top number (systolic) is the pressure when your heart beats and pushes blood out; the bottom number (diastolic) is the pressure between beats while the heart relaxes. A reading of 118/78 means systolic 118 and diastolic 78, both measured in millimetres of mercury.
What is mean arterial pressure?
Mean arterial pressure (MAP) estimates the average pressure driving blood to your organs over a full heartbeat. It's calculated as diastolic + (systolic − diastolic) ÷ 3, weighting the longer relaxation phase. A MAP around 70–100 mmHg is generally considered adequate for organ perfusion.
Is one high reading a problem?
Not necessarily. Blood pressure varies with stress, activity, and even the act of being measured (the 'white coat effect'). Diagnosis needs multiple readings over time, ideally including home measurements. A single high reading warrants rechecking, but a reading of 180/120 or above with symptoms is a medical emergency.