Blood Pressure Calculator

What Is Blood Pressure?

Blood pressure is the force exerted by circulating blood against the walls of your arteries. It is measured in millimeters of mercury (mmHg) and expressed as two numbers:

• Systolic pressure (SBP): The pressure when the heart beats and pumps blood out. This is the higher (top) number.
• Diastolic pressure (DBP): The pressure when the heart rests between beats. This is the lower (bottom) number.

A reading of 120/80 mmHg means a systolic pressure of 120 mmHg and a diastolic pressure of 80 mmHg.

How to Calculate Blood Pressure Parameters

Mean Arterial Pressure (MAP)

MAP represents the average arterial pressure throughout one cardiac cycle. It is a better indicator of tissue perfusion than systolic or diastolic pressure alone:

Or equivalently: MAP = (SBP + 2 × DBP) / 3

A normal MAP is typically between 70 and 100 mmHg. A MAP below 60 mmHg may not provide adequate perfusion to vital organs.

Pulse Pressure

Pulse pressure is the difference between systolic and diastolic pressure:

Normal pulse pressure is 40–60 mmHg. A wide pulse pressure (>60 mmHg) may indicate aortic regurgitation, arterial stiffness, or hyperthyroidism. A narrow pulse pressure (<25 mmHg) may suggest heart failure, aortic stenosis, or cardiac tamponade.

Blood Pressure Classification (ACC/AHA 2017)

Category	Systolic (mmHg)		Diastolic (mmHg)
Normal	< 120	and	< 80
Elevated	120–129	and	< 80
Stage 1 Hypertension	130–139	or	80–89
Stage 2 Hypertension	≥ 140	or	≥ 90
Hypertensive Crisis	> 180	and/or	> 120

European Classification (ESC/ESH 2018)

Category	Systolic (mmHg)		Diastolic (mmHg)
Optimal	< 120	and	< 80
Normal	120–129	and/or	80–84
High Normal	130–139	and/or	85–89
Grade 1 Hypertension	140–159	and/or	90–99
Grade 2 Hypertension	160–179	and/or	100–109
Grade 3 Hypertension	≥ 180	and/or	≥ 110

Hypotension (Low Blood Pressure)

Blood pressure below 90/60 mmHg is generally considered hypotension. Symptoms may include dizziness, fainting, blurred vision, nausea, and fatigue. Causes include dehydration, heart problems, endocrine disorders, severe infection (sepsis), blood loss, nutritional deficiencies, and certain medications.

Risk Factors for Hypertension

• Age: Risk increases with age, especially after 65
• Family history: Genetic predisposition plays a significant role
• Obesity: BMI >30 significantly increases risk
• Physical inactivity: Sedentary lifestyle raises risk by 20–50%
• Sodium intake: Excess salt causes fluid retention and increased BP
• Alcohol: Heavy drinking raises blood pressure
• Smoking: Nicotine temporarily raises BP; long-term use damages arteries
• Stress: Chronic stress contributes to sustained elevated BP
• Chronic conditions: Diabetes, kidney disease, sleep apnea

How to Measure Blood Pressure Correctly

1. Sit quietly for 5 minutes before measuring
2. Sit with your back supported, feet flat on the floor, legs uncrossed
3. Place the cuff on your bare upper arm, 1 inch above the elbow crease
4. Rest your arm on a flat surface at heart level
5. Do not talk during the measurement
6. Take 2–3 readings one minute apart and average them
7. Avoid caffeine, exercise, and smoking for 30 minutes before measuring

Frequently Asked Questions

What is a dangerous blood pressure level?

A reading above 180/120 mmHg is considered a hypertensive crisis and requires immediate medical attention. Symptoms may include severe headache, chest pain, shortness of breath, visual changes, or confusion.

What is MAP used for?

MAP is used clinically to assess organ perfusion pressure. It is especially important in critical care settings. A MAP of at least 60–65 mmHg is needed to adequately perfuse vital organs including the brain, heart, and kidneys.

Can blood pressure vary throughout the day?

Yes. Blood pressure naturally fluctuates — it tends to be lowest during sleep and highest in the morning shortly after waking. Physical activity, stress, caffeine, meals, and posture all affect readings. This is why consistent measurement conditions are important.