Reference library

Heart rate, HRV & SpO2 charts.

Reference charts for heart rate, variability, oxygen saturation, and related measurements. Read the source and the conditions behind every range.

Pulse Pressure: What It Is and What's Normal

Pulse pressure is the gap between the two numbers of a blood pressure reading: systolic minus diastolic. At a reading of 120/80 mmHg it is 40 mmHg, which reviews use as the typical resting value. This page explains the number; it does not give treatment advice.

Max Heart Rate Calculator by Age

Maximum heart rate is the highest rate your heart reaches during all-out exercise. Most people never measure it, so it is estimated from age. The calculator shows four published equations side by side, and the table lists the Tanaka estimate by age.

Normal Sleeping Heart Rate by Age and Sex

Heart rate falls during sleep, usually below a daytime seated pulse. The age and sex table is optical PPG data from rings, not a clinic study: Oura’s figures for 6 million members aged 18 to 70 in 2026, the night average and the overnight low.

Normal Walking Heart Rate by Age

There is no single measured heart rate for walking. Optical PPG readings from a phone, watch, or ring are usually compared with the moderate-intensity band, about 64 to 76% of estimated maximum heart rate. The tables convert that published band into beats per minute by age and sex.

Resting Heart Rate Chart by Age and Sex

The American Heart Association calls 60 to 100 beats per minute a normal resting heart rate for adults who are sitting or lying down, calm and well. That range is wide, so the percentiles below show where people actually fall. They come from NHANES 1999–2008: seated pulse measured after about four minutes of rest in people without a condition or medicine that changes pulse.

Normal Heart Rate by Age and Sex

Resting heart rate is highest in infancy and falls through childhood before levelling off near 70 beats per minute in adults. The percentile table is NHANES 1999–2008, males and females combined, a seated pulse (resting, for small children) in people without conditions or medicines that affect it. Use it as a population reference when you read an optical heart-rate number, not as a device specification.

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

For most adults, the AHA describes 60–100 BPM as the normal resting range. A number alone cannot identify the rhythm or determine whether cardioversion, pacing or defibrillation is appropriate. Symptoms and signs of poor perfusion drive emergency response; the bands below provide context rather than treatment thresholds.

VO2 Max Chart by Age and Sex

VO2 max is the most oxygen your body can use during all-out exercise, in millilitres per kilogram of body weight per minute (mL/kg/min). The percentiles below come from the FRIEND registry: 7,783 maximal treadmill tests with measured gas exchange in US adults aged 20 to 79 without cardiovascular disease. Enter your number to see where it falls for your age and sex.

Blood Pressure Chart: What the Numbers Mean

A blood pressure reading is two numbers in millimetres of mercury (mmHg): systolic, the pressure while the heart beats, over diastolic, the pressure while it rests between beats. The table shows the American Heart Association's categories for adults. When the two numbers fall in different rows, the higher row applies.

Normal Respiratory Rate by Age

Respiratory rate is the number of breaths in one minute at rest. Adults usually breathe 12 to 20 times a minute; babies breathe far faster, and the rate falls quickly over the first two years. The table pairs the ranges clinicians use with the source for each.

What Is a Good HRV? Normal HRV by Age

There is no universal good HRV number. The age table reports mean RMSSD from one 5-minute supine ECG study of healthy adults. A watch or ring uses a different window, sensor and algorithm, so its number will not match that table. The bands further down are consumer-facing illustrations, not validated health grades.

Average Sleep Duration by Age

How much sleep people need changes across the lifespan. The table below is the National Sleep Foundation's recommended range for each age group. It is a consensus from a panel review, not an average measured in one population, and individuals still vary.

Normal Sleep Stages Distribution Chart

Sleep architecture varies with age, health, medication, prior sleep and the scoring method. The proportions below are broad adult illustrations from polysomnography literature, not diagnostic targets for an individual or a consumer wearable.

HRV Chart by Age

Published short-term HRV norms (RMSSD, SDNN) by age group, with how wearables differ from lab ECG.

HRV Chart for Women

How HRV in women changes with age and across the menstrual cycle, pregnancy and menopause.

Blood Oxygen Level Chart

Normal SpO2 ranges by age and condition, and what low readings mean.

Pulse Oximeter Readings Chart

How to read the SpO2 and pulse numbers on a fingertip oximeter.

Perfusion Index

What the PI number on a pulse oximeter means, normal ranges and its clinical uses.