Blood Pressure Calculator

Every blood pressure reading is two numbers in millimeters of mercury (mmHg). The top number, systolic, is the pressure in your arteries while the heart contracts. The bottom number, diastolic, is the pressure while the heart relaxes between beats. A reading of 132/84 means 132 systolic and 84 diastolic.

Nearly half of US adults (48.1%, about 119.9 million people) have high blood pressure by the current definition, according to CDC, and only about one in four of them (22.5%) has it under control. Because high blood pressure usually causes no symptoms until it has done damage, as NHLBI puts it, knowing where your numbers fall is the whole point of checking.

The adult blood pressure chart

US guidelines sort adult readings into five groups. The table shows the office cutoffs from the guideline and the home cutoffs that follow from its table of corresponding home values.

Look at the middle column. Only the first two rows need both numbers to fit ("and"). From stage 1 upward, one number is enough ("or"). That is the higher-category rule in the guideline: when systolic and diastolic fall in different categories, the reading belongs to the higher one. A high systolic number with a normal diastolic, such as 150/72, is called isolated systolic hypertension; the opposite pattern, such as 118/84, is isolated diastolic hypertension. Both count.

Worked example: averaging two readings

You sit quietly, take a reading of 134/86, wait a minute and take a second of 130/82. The calculator averages each number on its own: (134 + 130) ÷ 2 = 132 systolic and (86 + 82) ÷ 2 = 84 diastolic. Systolic 132 falls in the 130 to 139 band and diastolic 84 in the 80 to 89 band, so both numbers point to stage 1 hypertension.

To leave stage 1, the average would need to drop below 130 systolic and below 80 diastolic at the same time. This is exactly the calculator's default input, so you can follow every step on screen; the two single readings give MAPs of 102.0 and 98.0.

Worked example: a wide gap, 148/72

A 70-year-old gets a reading of 148/72. The diastolic number alone would be normal, but systolic 148 is above 140, so the reading is stage 2 hypertension, set by the systolic number. Pulse pressure is 148 − 72 = 76 mmHg, nearly double the 40 of a 120/80 reading. MAP is 72 + 76 ÷ 3 = 97.3 mmHg by the classic formula and 72 + 0.412 × 76 = 103.3 by the alternative weighting.

This example shows why MAP alone can mislead. A MAP of 97 looks unremarkable, almost the same as the 100 in the first example, yet this reading is a full category higher. MAP compresses two numbers into one and hides the wide gap that is often the most informative part of an older adult's reading.

Mean arterial pressure: the formula

Mean arterial pressure (MAP) estimates the average pressure in your arteries across one full heartbeat. Because the heart spends roughly two thirds of each beat relaxing at a normal resting rate, the average sits closer to the diastolic number than to the midpoint:

The one-third rule is the textbook version and the one most MAP calculators use. A 2016 study of 1,878 people by Papaioannou and colleagues compared seven ways of calculating MAP and found that the 0.412 weighting tracked markers of heart and artery damage more closely than the traditional one third, so the calculator shows both. MAP matters most in hospitals: the Surviving Sepsis Campaign recommends an initial target of 65 mmHg for adults in septic shock on vasopressors, for example.

MAP and pulse pressure for common readings

Every value below was computed with the same formulas the calculator uses. The category column applies the office chart and the higher-category rule.

Two rows deserve a second look. The 135/75 reading has a lower MAP than 128/82 despite a higher systolic number, and 165/72 has a lower MAP than 142/88 despite being far more elevated at the top. Pulse pressure is what separates them: 93 mmHg for 165/72. In the Framingham Heart Study, among adults aged 50 to 79 who were not on blood pressure medicine, a wider pulse pressure predicted coronary heart disease at least as well as either number on its own.

What the 2025 guideline changed, and what it kept

In August 2025 the American Heart Association, the American College of Cardiology and eleven other organizations published a new high blood pressure guideline. The categories and cutoffs did not change: normal, elevated, stage 1 and stage 2 keep the 2017 numbers, and hypertension still starts at 130/80. The main changes are about what happens next:

• "Hypertensive urgency" became severe hypertension: above 180/120 without signs of acute organ damage, to be treated promptly as an outpatient. With organ damage it is a hypertensive emergency, for which admission to intensive care is recommended.
• Risk is estimated with the PREVENT equations instead of the older pooled cohort equations.
• Stage 1 calls for medication if you have cardiovascular disease, diabetes, chronic kidney disease or a 10-year PREVENT risk of 7.5% or more; otherwise after 3 to 6 months of lifestyle changes if readings stay at 130/80 or higher.
• Stage 2 calls for medication for everyone, usually two drugs from different classes, preferably in a single pill.
• Home or ambulatory readings are recommended to confirm a suspected diagnosis, as in 2017, and home monitoring gets a larger role in ongoing care. The treatment goal stays under 130/80, with encouragement to reach under 120/80.

Home readings versus office readings

Readings taken at home tend to run differently from office readings, so the guideline publishes a table of matching values. At 120/80 and 130/80 the home and office numbers are the same. Higher up they diverge: an office reading of 140/90 corresponds to 135/85 at home, and 160/100 corresponds to 145/90. When you choose "Home monitor" in the calculator, stage 2 therefore begins at 135/85.

Here is how that plays out. Three morning readings at home of 138/84, 134/82 and 133/80 average to 135/82. On the office chart that would be stage 1, because 135 is under 140 and 82 is under 90. On the home chart it is stage 2, because the home systolic of 135 already matches an office 140. MAP is 99.7 and pulse pressure 53 either way.

Home monitoring also catches two patterns that a single office visit can miss. In white coat hypertension, readings are high in the clinic but normal at home; in masked hypertension, they look normal in the clinic and run high in daily life. A 2026 review of the new guideline points out that both the 2017 and the 2025 versions stress ruling out a white coat effect before treatment is stepped up, and the 2025 guideline recommends home or ambulatory readings to confirm a suspected diagnosis.

How to measure your blood pressure accurately

A calculator can only be as good as the reading you type in. CDC's home measurement steps:

1. Do not eat or drink anything for 30 minutes beforehand, and avoid smoking, alcohol, caffeine and exercise in that window, since each can raise the result.
2. Empty your bladder, then sit in a chair with your back supported for at least 5 minutes.
3. Keep both feet flat on the floor and your legs uncrossed.
4. Rest the arm with the cuff on a table at chest height, with the cuff snug against bare skin, not over clothing.
5. Do not talk during the measurement.
6. Take at least two readings 1 or 2 minutes apart, at the same time every day, and record them in a log.

NHLBI adds that home readings should come from an approved home blood pressure device, and that a diagnosis needs two or more readings at separate appointments.

How to use this calculator

1. Choose where you measured. "Doctor's office" applies the standard chart; "Home monitor" applies the home equivalents.
2. Enter each reading. Type the systolic and diastolic numbers. Add up to six readings with the button below the list.
3. Read the headline. It shows the average, rounded to whole mmHg, and the category badge.
4. Check the tiles. They show MAP, pulse pressure and which number set your category.
5. Look below. The colored card explains the category and what would move you down one; the tables list each reading and the full chart.

Who this calculator is for

It suits adults tracking their own blood pressure at home, people who just came back from a checkup with two numbers and a vague comment, and family members helping an older parent keep a log. Nursing, EMT and physiology students can use the MAP section to check their work with the one-third formula taught in class. Clinicians can use it for a quick category and MAP check, but it is not built for treatment decisions, pregnancy or children.

Key terms

• Systolic (SBP): the top number, pressure during a heartbeat.
• Diastolic (DBP): the bottom number, pressure between beats.
• mmHg: millimeters of mercury, the unit for blood pressure.
• Mean arterial pressure (MAP): the estimated average pressure across one heartbeat.
• Pulse pressure: systolic minus diastolic. Not the same as pulse, which is heart rate.
• Isolated systolic hypertension: high systolic with diastolic under 80.
• Severe hypertension: above 180/120 without acute organ damage (the 2025 term).
• Hypotension: low blood pressure, described by NHLBI as lower than 90/60.

Limitations

The categories come from the adult guideline. Children are judged against pediatric percentile tables, and for teens 13 and older the 2017 American Academy of Pediatrics guideline uses a simplified classification that lines up with the adult cutoffs. The calculator cannot tell whether your cuff fits, whether your device is validated or whether you rested first, and readings vary from minute to minute and from day to day. MAP and pulse pressure computed from a cuff are estimates; in intensive care they are measured continuously through an arterial line. Readings from cuffless gadgets such as some watches and rings are a further step removed: the 2025 guideline does not recommend them for diagnosing or treating high blood pressure. Most importantly, a category is not a diagnosis. Diagnosis rests on repeated readings, ideally confirmed outside the office, and treatment depends on your overall cardiovascular risk, which needs a clinician.

Related calculators

• Drinking less alcohol is one of the guideline's lifestyle steps. See how drinks turn into blood alcohol with the BAC Calculator.
• Belly fat and blood pressure often travel together. Check your waist-to-height ratio or the Waist-to-Hip Ratio Calculator.
• For weight relative to height, use the BMI Calculator.
• Heart rate is a different number from blood pressure. Find your training zones with the Target Heart Rate Calculator.
• If your clinician suggests losing weight, plan it with the Weight Loss Calculator.

Sources

• Jones DW, Ferdinand KC, Taler SJ, et al. (2025), "2025 AHA/ACC/AANP/AAPA/ABC/ACCP/ACPM/AGS/AMA/ASPC/NMA/PCNA/SGIM Guideline for the Prevention, Detection, Evaluation and Management of High Blood Pressure in Adults," Hypertension 82(10):e212-e316, PubMed.
• Whelton PK, Carey RM, Aronow WS, et al. (2018), "2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults," Hypertension 71(6):e13-e115, PubMed.
• Brown C, Clark D, Jones DW (2026), "Updates in the 2025 AHA/ACC Hypertension Guideline," Current Hypertension Reports, PubMed.
• National Heart, Lung, and Blood Institute (NHLBI, NIH), High Blood Pressure: Diagnosis (category table, two or more readings), Symptoms (180/120 and when to call 911) and Low Blood Pressure (below 90/60).
• Centers for Disease Control and Prevention (CDC), Measuring Your Blood Pressure and High Blood Pressure Facts.
• Papaioannou TG, Protogerou AD, Vrachatis D, et al. (2016), "Mean arterial pressure values calculated using seven different methods and their associations with target organ deterioration in a single-center study of 1878 individuals," Hypertension Research, PubMed.
• Franklin SS, Khan SA, Wong ND, et al. (1999), "Is pulse pressure useful in predicting risk for coronary heart disease? The Framingham Heart Study," Circulation, PubMed.
• Flynn JT, Kaelber DC, Baker-Smith CM, et al. (2017), "Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents," Pediatrics, PubMed.
• Evans L, Rhodes A, Alhazzani W, et al. (2021), "Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021," Intensive Care Medicine, PubMed.