Example: Male, 38, 80kg, 178cm

A 38-year-old male, 80kg, 178cm, wrist 17.5cm (normosthenic), resting heart rate 68 bpm, owl chronotype, actual BP 128/82:

• Body Surface Area (Mosteller): 2.00 m²
• Blood Volume (Nadler): ~5.8 L — about 7 standard bottles
• Vascular Stiffness Index: 4.2/10 — moderate
• Chronotype correction: +3 mmHg (owl — higher evening BP)
• Frame correction: 0 mmHg (normosthenic)
• Personalized optimal BP: ~122/80 mmHg
• Vascular age: 41 — 3 years above chronological
• Pulse pressure: 42 mmHg — upper boundary, monitor
• PNI: +6/+2 mmHg — mild elevation above personal optimum

Why 120/80 Is Not Your Number

The standard 120/80 mmHg guideline is a population average. It says nothing about what your individual optimal pressure should be. A petite 45kg woman and a 100kg athlete should not have the same target. A morning person and a night owl have different BP rhythms. Someone with a lean bone frame naturally runs lower than someone with a large frame.

This calculator accounts for all of these factors — producing a personalized norm rather than a population average.

The Science Behind the Calculation

Body Surface Area (Mosteller formula) is a standard clinical measurement used in cardiology. Larger bodies require more cardiac work, reflected in slightly higher optimal pressures. The Nadler equation estimates circulating blood volume — which directly affects preload and optimal BP. Chronotype corrections are based on established circadian BP research: blood pressure follows its own daily rhythm, and owls in particular run a delayed cycle that shows up as higher readings in the evening — a pattern that’s normal for their biology but can look artificially elevated if a clinical measurement happens to be taken in the morning instead. Frame type from wrist circumference adjusts for structural differences in hemodynamic requirements.

The Vascular Stiffness Index shown in the results is a proxy score from 0 to 10, estimated from age, BMI, and wrist circumference rather than measured directly — higher scores point toward less elastic arteries. It’s a useful directional signal, but true arterial stiffness is only measured clinically, via pulse wave velocity, and this proxy isn’t a substitute for that measurement.

Pulse Pressure as a Vascular Health Marker

Optimal pulse pressure is 30–40 mmHg. Above 55 mmHg it becomes an independent predictor of cardiovascular events. Below 30 mmHg may indicate reduced cardiac output. Your pulse pressure is calculated from your personalized optimal BP, not from the standard 120/80.

Reading the Personalized Norm Index

The PNI card above only appears once an actual measured BP has been entered, and it exists to answer one question: how far is that real reading from your calculated personal optimum, not from the generic 120/80. A deviation of roughly ±5 mmHg systolic and ±4 mmHg diastolic sits within the expected range for normal day-to-day variation; deviations meaningfully larger than that suggest the measured BP is running above or below what this specific hemodynamic profile predicts as optimal, which is worth raising with a doctor rather than something to self-manage from this page alone.