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You already own the sensor. Sixteen turns your Apple Watch into a health system.
Wear the watch to bed and every morning you get a recovery score, a sleep score and a strain target, the way strap and ring owners do. No new hardware. No membership.
How it connects
The data path, exactly.
Apple Watch writes heart rate, HRV, respiratory rate, sleep stages, workouts, steps and energy to Apple Health on your iPhone. Sixteen reads those with your permission, on the device.
Setup
- Install Sixteen on your iPhone.
- In setup, choose Apple Watch and allow the Apple Health categories Sixteen asks for.
- Wear the watch to bed tonight. Tomorrow morning the scores appear.
What comes across
- Sleep stages and duration
- Overnight HRV (SDNN samples)Baseline builds over the first week
- Resting and all day heart rate
- Respiratory rateSeries 8 and later, worn to bed
- Workouts with heart rate
- Steps, active energy, cardio fitness
- Beat to beat intervalsApple Health exposes HRV summaries, not raw intervals
Good to know
- Wear the watch overnight at least five nights a week for a stable baseline.
- Sixteen shows a learning state for the first few nights.
- Nothing leaves your phone unless you turn on cloud backup.
Questions people ask
Is there a recovery score on Apple Watch?
Not built in. Apple Health stores HRV, resting heart rate, sleep and respiratory rate; the Vitals app flags outliers. Sixteen reads those and computes a daily recovery percentage against your own baseline.
Is there a WHOOP app for Apple Watch?
WHOOP does not make one. Sixteen gives an Apple Watch the same morning answer, recovery, strain and sleep, from Apple Health data, and it also reads a WHOOP strap directly.
Does Apple Watch track HRV?
Yes, as SDNN samples taken mostly overnight, stored in the Health app under Heart Rate Variability. Wear the watch to bed so the calm overnight samples are captured; Sixteen builds a baseline from them.
Can I use my Apple Watch like a WHOOP?
For the daily question WHOOP answers, how recovered am I and how hard should I go, yes. Sixteen gives you a recovery percentage, a strain target and a sleep score from Apple Watch data. WHOOP's strap has its own advantages, such as being screenless and lasting days on a charge.
Which Apple Watch models work?
Any Apple Watch that writes sleep and heart rate to Apple Health. Respiratory rate needs Series 8 or later, or an Ultra.
Do I need Apple Fitness+ or any Apple subscription?
No. Apple Health is free and Sixteen is a one time purchase or a monthly plan with no wearable membership.
Does Sixteen drain the watch battery?
No. Sixteen never runs on the watch. It reads what the watch already records.
SixteenPay once. Keep your data. Earn your scroll.
Sixteen is $99 once for lifetime access, or $19.99 a month. Connect the wearable you already own. No hardware to buy, no membership that expires.
iPhone (iOS 17 or later). Prices in USD.