WRISTGRID BLOG
How Garmin Body Battery is calculated
Body Battery is one of Garmin's most-loved metrics: a single 0–100 number for "how much energy do I have left?" But it's also one of the least understood. Here's what's actually going on under the hood — and how to read yours like a coach would.
What Body Battery actually measures
Body Battery is Garmin's energy-monitoring score, developed with Firstbeat. It combines your heart-rate variability (HRV), stress, sleep quality, and activity into one number between 0 and 100. Think of it as a fuel gauge for your body: it charges when you rest and drains when you're active or stressed.
A score near 100 means you're fully charged and ready for a hard effort. A score near 0 means your body is depleted and prioritizing recovery. Most people wake up somewhere in the 70–100 range after a good night and drain through the day.
The signals behind the number
Body Battery is proprietary — Garmin doesn't publish the exact formula. But it's built on well-documented physiology. The core input is heart-rate variability: the tiny variations in time between your heartbeats. High HRV (more variation) signals a relaxed, recovered state dominated by your parasympathetic nervous system. Low HRV signals stress or fatigue.
During the day, physical activity and physiological stress drain your battery. During sleep and genuine rest, it recharges. That's why a stressful work meeting can drain your battery almost as much as a light workout — your body doesn't distinguish much between physical and psychological stress; both show up in your HRV.
Why your Body Battery feels "wrong" sometimes
A common frustration: you sleep eight hours but wake up at 60. Usually the cause is late alcohol, a late hard workout, illness coming on, or a genuinely stressful day — all of which suppress overnight HRV and slow your recharge. The number isn't broken; it's reflecting that your nervous system didn't fully downshift overnight.
This is also why Body Battery works best as a personal baseline, not a competition. Your 80 and a friend's 80 aren't the same thing — the metric adapts to your own physiology over time.
How to use it (without obsessing)
Use Body Battery as a conversation with your body, not a judge. A high morning score is a green light for a hard session. A low score is a nudge toward rest, easy movement, or an earlier night. Over weeks, you'll start to see which habits — late screens, alcohol, evening workouts — cost you the most charge.
And because it updates through the day, it's most useful at a glance. That's exactly why WristGrid puts your Body Battery on your iPhone Home Screen and Lock Screen: you can see your energy level without opening an app, synced automatically from your watch.
NEXT STEP
Put your Garmin metrics on your iPhone.
Now on the App Store