WHOOP Accuracy: Industry-Leading HR & HRV Measurements

When it comes to understanding your body, the quality of your data is important. Actionable insights and personalized recommendations depend on a foundation of accurate, reliable measurements. Independent, third-party studies confirm that WHOOP provides industry-leading accuracy for the physiological data that matters most.

The foundation of personalized coaching is accuracy

Wearable technology gives you the power to better understand your body and improve your health. However, recommendations across sleep, strain, and recovery are only as good as the data they are built on. Heart rate (HR) and heart rate variability (HRV) are the two physiological metrics at the core of WHOOP scores.

The Australian Institute of Sport (AIS) funded an independent, third-party study conducted by Central Queensland University (CQUniversity), published in Sensors, examining the accuracy of six wearable devices. The study found that WHOOP is 99.7% accurate in measuring heart rate and 99% accurate in measuring heart rate variability. By contrast, other wearables scored between 41% and 96% in HR accuracy and 24% and 69% in HRV accuracy.

CQUniversity independently examined the validity of six commonly used wearables (WHOOP, Oura Ring, Apple Watch, Garmin Forerunner, Polar Vantage, and Somfit) for assessing sleep, heart rate, and heart rate variability during sleep. Participants were fitted with all six wearable devices along with ECG and polysomnography (PSG), the gold-standard of sleep tracking. By having every participant wear all devices simultaneously, this research provides a clean view of how each wearable performs under equivalent conditions.

How WHOOP measures heart rate with industry-leading accuracy

The CQUniversity study found that WHOOP was the most accurate of the wearables evaluated in measuring HR compared to gold-standard ECG-derived heart rate. WHOOP had the smallest errors in measurement with a standard deviation of 1 beat per minute (bpm) while other wearables ranged from 2.1 to 12.8 bpms.

A Bland-Altman plot visualizes the differences between two quantitative measurements. In the below analysis, the X-axis shows the gold-standard measured data and the Y-axis shows the difference between that standard and what each device reported.

Data clustering along the flat line at zero were perfect (the device calculated the same value as ECG) and errors are shown above and below that line. In comparison to other leading wearables, WHOOP clearly delivered the most accurate HR measurements.

Validating heart rate variability for a precise look at recovery

The CQUniversity study confirmed that WHOOP delivered the most accurate heart rate variability (HRV) measurements. WHOOP had the smallest error in HRV with a standard deviation of 3.9 milliseconds (ms) while other wearables ranged from 28.1 to 46.9 ms.

The analysis shows that WHOOP excelled in measuring HRV while other wearables were unreliable compared to gold-standard. Several other wearables struggled to measure higher HRVs — with some underestimating values by 200 ms. The highly accurate WHOOP readings ensure the data guiding your Recovery is a true reflection of your body's readiness to perform.

In a second independent study, AIS sought to determine the reliability of HR and HRV measurements by WHOOP to gauge readiness to perform in everyday use. Researchers monitored athletes wearing WHOOP over 16 weeks, comparing WHOOP automated readings to manual data collection. According to the study findings, "WHOOP allows for frequent and convenient measurement of HR and HRV" and can be "confidently utilised by sport and exercise science practitioners to record HR and HRV in practical settings."

Measuring sleep with gold-standard accuracy

Researchers tested sleep tracking capabilities compared to gold-standard PSG data. WHOOP and other devices calculate sleep via photoplethysmography (PPG), a technique that measures blood flow by assessing superficial changes in blood volume. Once blood flow is measured, we derive heart rate, heart rate variability, and respiratory rate, all of which are used in the WHOOP sleep detection and staging algorithm.

Among all wearables in the study with PPG sensors, WHOOP had the greatest agreement with gold-standard PSG for REM and slow wave sleep (SWS) measurements. WHOOP was found to be excellent in identifying sleep overall.

In reviewing the four stages of sleep, REM sleep is when your brain is restored and SWS sleep is when your muscles repair and grow. Those two stages make up restorative sleep which is essential for recovery. This precision allows WHOOP to provide actionable, personalized insights to help you improve your sleep quality and overall health.

How accurate data powers your WHOOP insights

Accurate measurement of HR and HRV is the first step. The real power comes from translating that data into personalized insights. Your daily Strain and Recovery scores are calculated using your precise HRV and heart rate data, while Sleep Performance is determined by how accurately WHOOP measures your sleep cycles.

How to get the most accurate data from your WHOOP

To ensure you get the highest quality data, proper wear is key. Your WHOOP should be worn snugly on your non-dominant wrist, about one inch above your wrist bone. During intense activity involving significant wrist flexion, moving the device further up your arm can improve consistency.

Keeping the sensor clean and dry helps maintain a strong signal for precise measurements.

The commitment to continuous improvement

The validation provided by both studies from the Australian Institute of Sport underscore the quality of WHOOP measurements. We've built upon the industry-leading accuracy in WHOOP 3.0 as a foundation for WHOOP 4.0, 5.0 and MG. The 4.0 sensor configuration contains 5 LEDs (three green, one red, and one infrared) and 4 photodiodes to further improve accuracy.

Research and development was conducted at WHOOP Labs and in real-world environments to test WHOOP 4.0 against a variety of member use cases. Diversity in study participants was essential to ensure optimal performance across ages, body types, fitness levels, skin tones, genders, and handedness. Thousands of people participated in data collections prior to launch, resulting in more than 20,000 data sets pairing WHOOP with chest straps and ECGs.

WHOOP continues to invest in ongoing studies to develop new features and enhance proprietary algorithms. This commitment to science ensures you can trust WHOOP to help you understand your body.

Frequently asked questions about WHOOP accuracy

How does WHOOP accuracy compare to other wearables?

An independent study conducted by Central Queensland University found WHOOP to be the most accurate wearable for measuring heart rate and heart rate variability when compared to several other popular devices. The study used gold-standard ECG and PSG measurements as the benchmark for comparison.

What can I do if my data seems inaccurate?

If you have concerns about your data, first ensure your device is worn correctly — snug and properly placed on your wrist. You can also try cleaning the sensor. For activities with a lot of wrist motion, consider using WHOOP Body apparel or moving the device higher up your arm.

*When compared to the gold-standard electrocardiogram-derived (ECG) metrics