How Does Garmin Measure Body Battery?

Just like body composition analysis is a prime selling point of the Samsung Galaxy Watch 7, Garmin Body Battery (available on most current models) is a key feature on the brand's smartwatches that helps you manage your health. Similar to how a smartphone's battery gauge lets you know how much energy is available for your device, Garmin Body Battery  shows your body's energy level throughout the day as a score between zero and 100, where zero indicates you're completely drained  and 100 means you're fully rested. 

Just like watching a movie or gaming drains your smartphone's battery, physically or mentally demanding tasks have a similar effect on your Body Battery level. Garmin Body Battery uses sensors for blood oxygen levels, motion, and heart rate to evaluate your body's condition and stress levels. The feature feeds multiple data streams from sensors on the smartwatch into an algorithm that processes the numbers to give you an idea of your body's current condition. This can help you track patterns throughout the day and week that might prompt changes in your routine.

Garmin smartwatches constantly monitor various data points to determine your resting heart rate and oxygen levels and how they change during different activities or times of day. This information is combined with movement and sleep data and processed by an algorithm developed by Firstbeat Analytics, a sports science company Garmin acquired in 2020. The algorithm establishes a baseline for how your body functions and uses this to track your body's condition as you go about your activities.

An elevated heart rate along with movement signals physical activity, while a slightly raised heart rate without movement might indicate stress during the day or a restless period during sleep. Using Garmin's heart rate variability (HRV) status feature, the algorithm can also identify other moments that tax or rejuvenate your body. To put things most simply, the algorithm then compares each moment's data to your baseline metrics to estimate how much energy your body has used. You current condition is calculated and shown as your Body Battery score, which keeps changing throughout the day and night.

Your Garmin Body Battery score should be highest in the morning right after waking up. Depending on your sleep quality, the score could be a perfect 100 or lower due to factors like stress, illness, or alcohol consumption. As you go about your daily activities, the various active physiological states your body goes through will affect your Body Battery differently. Meanwhile, resting will slow down your rate of energy consumption, and a nap might even give your Body Battery level a slight boost.

Any physical activity will drain your Body Battery, and how fast his happens depends on the intensity and duration of the activity. Mental stress from nervousness, hyper-vigilance, or worrying about a situation also runs down your Body Battery. Garmin uses a separate 0-100 scale to track your stress; anything higher than 25 depletes your Body Battery score even in the absence of physical activity. Similarly, lower stress levels will keep your Body Battery score high even if you're active. Consistent, quality sleep plays the most significant role in replenishing your Body Battery score, which is why it's usually highest in the morning. But if you don't get enough sleep or you're stressed while sleeping, your body and Body Battery score might not recover fully overnight. 

The score is closely related to your baseline fitness levels as well. When you're in good shape, your body can handle physical activity and mental stress more efficiently; this slows down energy drain and helps you recover faster. Garmin uses VO2 max — a calculation of heart health based on oxygen consumption — to find out how hard your body is working during exercise. This factor is taken into account in figuring out how fast your energy is being depleted or restored. If your fitness levels change over time, the algorithm adapts accordingly. Now that you know how the hardware and software pieces that make up Garmin's Body Battery system give you real-time insights into how well your body is handling everyday tasks, you can better understand what recharges and drains you and make the most out of that information.