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Health Reference Charts

Evidence-based reference charts and data tables for heart rate variability, blood oxygen levels, resting heart rate, blood pressure, and other vital sign ranges.

Heart Rate Variability (HRV) Chart by Age

Heart rate variability (HRV) is a measure of the variation in time between consecutive heartbeats, reflecting autonomic nervous system function. HRV naturally declines with age as parasympathetic tone decreases. This chart presents normal RMSSD and SDNN ranges by age group based on large-scale population studies.

HRV Chart for Females by Age

Heart rate variability differs between sexes, with females generally showing slightly lower SDNN but comparable or higher RMSSD values than males in younger age groups. Hormonal fluctuations across the menstrual cycle, pregnancy, and menopause significantly influence female HRV patterns. This chart provides female-specific normative HRV ranges based on published sex-stratified population data.

Pulse Oximeter Readings Chart

A pulse oximeter measures peripheral oxygen saturation (SpO2), estimating the percentage of hemoglobin molecules carrying oxygen in arterial blood. Normal SpO2 for most healthy adults is 95–100%. This chart explains what each SpO2 reading means clinically, from normal to critical levels requiring emergency intervention.

Blood Oxygen Level Chart

Blood oxygen levels, measured as SpO2 (peripheral oxygen saturation), reflect how effectively your lungs transfer oxygen to your bloodstream. Understanding your blood oxygen level is essential for managing respiratory conditions including COPD, asthma, COVID-19 pneumonia, and heart failure. This chart categorizes SpO2 ranges by clinical significance.

Resting Heart Rate Chart by Age and Fitness Level

Resting heart rate (RHR) is a fundamental cardiovascular health indicator, measured in beats per minute (BPM) while at complete rest. A lower resting heart rate generally indicates more efficient cardiac function and better cardiovascular fitness. This chart categorizes resting heart rate by age group and fitness level based on established norms from the American Heart Association.

Normal SpO2 Levels by Age and Condition

Normal blood oxygen saturation (SpO2) varies by age, altitude, and underlying health conditions. While 95–100% is the standard reference range for healthy adults at sea level, certain populations have different expected baselines. This chart provides condition-specific SpO2 ranges to help you interpret pulse oximeter readings in the appropriate clinical context.

HRV Chart for Males by Age

Heart rate variability in males follows a predictable age-related decline, though men tend to have slightly higher SDNN and overall HRV variability compared to women in most age groups. Male HRV is influenced by factors such as testosterone levels, body composition, fitness level, and cardiovascular health. This chart provides male-specific normative HRV data from population-based studies.

Heart Rate Training Zones Chart

Heart rate training zones divide your exercise intensity into five distinct zones based on percentage of maximum heart rate (%MHR). Each zone elicits different physiological adaptations and energy system usage. Understanding your training zones enables targeted workouts for fat burning, aerobic endurance, lactate threshold, or peak performance improvement.

Dangerous Heart Rate Levels Chart

While resting heart rate normally ranges from 60 to 100 BPM, values outside this range may indicate a cardiac emergency or underlying condition requiring medical evaluation. Both abnormally slow (bradycardia) and abnormally fast (tachycardia) heart rates can be dangerous depending on the clinical context. This chart helps identify when heart rate values require urgent medical attention.

VO2 Max Chart by Age and Gender

VO2 max (maximal oxygen consumption) is the gold standard measure of cardiorespiratory fitness, expressed in mL/kg/min. It represents the maximum rate at which your body can use oxygen during intense exercise. Higher VO2 max values are strongly associated with reduced cardiovascular mortality and all-cause mortality. This chart classifies VO2 max by age, gender, and fitness level based on ACSM normative data.

Blood Pressure Ranges Chart

Blood pressure is recorded as two numbers: systolic (pressure during heartbeats) over diastolic (pressure between heartbeats), measured in millimeters of mercury (mmHg). The American Heart Association classifies blood pressure into five categories that guide treatment decisions. Hypertension is a leading risk factor for heart attack, stroke, kidney disease, and heart failure.

Normal Respiratory Rate by Age

Respiratory rate (breaths per minute) is a vital sign that reflects pulmonary function, metabolic status, and neurological control of breathing. Often called the 'neglected vital sign,' an abnormal respiratory rate is one of the earliest indicators of clinical deterioration. This chart provides age-specific normal ranges based on WHO and pediatric clinical guidelines.

What Is a Good HRV Score?

Heart rate variability (HRV) scores from wearable devices can be confusing without context. There is no single 'good' HRV number because optimal values vary by age, sex, fitness level, and measurement method. This chart provides general interpretation guidelines for RMSSD-based HRV scores, the metric most commonly reported by consumer wearables like Apple Watch, Whoop, and Oura Ring.

Normal Sleep Stages Distribution Chart

Sleep is composed of distinct stages that cycle throughout the night, each serving different restorative functions. Understanding normal sleep stage distribution helps you interpret data from sleep trackers like Oura Ring, Whoop, Fitbit, and Apple Watch. Deviations from normal patterns may indicate sleep disorders, stress, or lifestyle factors affecting sleep quality.

Perfusion Index Normal Ranges

The perfusion index (PI) is a numerical value displayed on many pulse oximeters that indicates the ratio of pulsatile to non-pulsatile blood flow at the sensor site. PI reflects peripheral perfusion strength and can provide insights into cardiovascular status, hydration, and local blood flow. A higher PI indicates stronger peripheral pulse amplitude, while a very low PI may indicate poor perfusion or signal quality issues.