Garmin vs Whoop: 100 days HRV & RHR data comparison

In this article, I delve into a comparison between the heart rate variability (HRV) and resting heart rate (RHR) readings of the Garmin Forerunner 955 and Whoop 4.0, two devices that I have been using for a considerable amount of time. Read on to find out how they stack up against each other.

Why is HRV important?

Most people are aware of what RHR is. So for the purposes of this article, I will not delve into this. You can read more about it in our separate article on the topic.

But what about HRV? Why is it important?

HRV represents the variations in time between successive heartbeats, measured by RR intervals. Higher HRV values suggest better cardiovascular health, while lower values may indicate increased sympathetic nervous system activity and reduced parasympathetic nervous system activity. However, it’s essential to remember that HRV can vary significantly among individuals due to factors like age, sex, and genetics. The focus should be on HRV trends rather than individual readings.

RR intervals
RR intervals | Image source: Whoop

To establish a baseline HRV, wearables monitor users’ HRV readings over several days or weeks. This baseline can then be used to provide insights into an individual’s cardiovascular health and stress level changes.

How Whoop and Garmin calculate HRV

Both Whoop and Garmin leverage HRV to provide personalised recovery data, including rest, optimal training intensities, and stress management techniques. Athletes and individuals undergoing physical training can benefit from this data, allowing them to optimize their training routines and minimize the risk of injury or burnout.

Normal HRV by age
Image source: Whoop

Just like Garmin, Whoop measures HRV using a photoplethysmography (PPG) sensor, which calculates R-R intervals by detecting changes in blood volume in capillaries under the skin. The device then employs various algorithms to derive HRV metrics, including time domain analysis, frequency domain analysis, and non-linear analysis. While Whoop initially relied on data from the last slow wave sleep stage for HRV calculations, recent updates suggest that Whoop now uses a dynamic average throughout the night, emphasizing data collected during deep sleep phases.

Essential readingTop fitness trackers and health gadgets

Garmin, on the other hand, calculates HRV as an average of RMSSD for the entire night’s data. This approach is pretty much in line with Whoop’s updated method.

Garmin vs Whoop: 100 days RHR comparison

The important question is to do with the actual data – how do figures churned out by Garmin devices compare with Whoop? I’ve had a Forerunner 955 on my left wrist and Whoop 4.0 on my right wrist for almost six months now. Tracking activity and sleep each and every day.

In this article I compare 100 days of HRV and resting heart rate (RHR) data. During this period I was actively training for the Paris marathon on the 2nd of April. So I was putting my body through quite a stressful period.

Let’s start off with RHR first.

Whoop dished out consistently higher figures than the Garmin, most likely because it calculates RHR differently. There’s nothing strange about this- different companies have their own algorithms for this metric.

During the 100 day period, the average RHR calculated by Whoop was 56 beats per minute (BPM). That is 4 bpm higher than the Garmin which averaged me at around 52 bpm.

Garmin vs Whoop - RHR comparison

Here’s a chart showing the 7 day RHR moving average for both devices. It shows a very strong correlation.

Garmin vs Whoop - RHR comparison

Garmin vs Whoop: 100 days HRV comparison

What about HRV? This comparison will probably interest more people. Here are the same two charts.

Examining the raw data, it is evident that Whoop’s HRV data was predominantly lower than the figures produced by the Garmin device. However, it’s worth noting that Whoop’s data demonstrated greater reactivity, with its peaks generally surpassing those of Garmin, and its troughs dipping lower.

On average, Whoop HRV average for this 100 day period was 32ms, Garmin’s average was 36ms.

Garmin vs Whoop - HRV comparison

Below is a chart showing the 7 day moving average. What is evident from this is that despite the above mentioned differences, HRV trends data was mostly in line. Not as much as RHR, but still similar. Which is important because it shows that both devices can be used to monitor how your HRV is changing over time.

Garmin vs Whoop - HRV comparison


The comparison between the Garmin Forerunner 955 and Whoop 4.0 revealed some differences in the raw data collected by each device. However, the trends and patterns observed in both HRV and RHR data were quite consistent across both wearables, indicating that either device can be effectively used to monitor changes in an individual’s cardiovascular health and stress levels over time.

Although the devices employ different algorithms and methods to calculate HRV and RHR, they both utilise this data to provide personalised recovery insights and recommendations. I would say that Whoop is stronger in the way it displays these figures and the types of insights it provides. It also dishes out more accurate sleep data. Garmin, on the other hand, is the more complete solution if you are looking for a proper sports watch.

Check out our hands-on review of the Garmin Forerunner 955 on this link. Our Whoop 4.0 hands-on review can be found here.

Like this article? Subscribe to our monthly newsletter and never miss out!

Marko Maslakovic

Marko founded Gadgets & Wearables in 2014, having worked for more than 15 years in the City of London’s financial district. Since then, he has led the company’s charge to become a leading information source on health and fitness gadgets and wearables.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.