Guides
The blog explains what HRV is and where it breaks down. These guides are the hands-on half: what to actually do with your watch, your wrist and your week to get numbers worth reading.
UPDATED 2 SEPTEMBER 2026
Wear position, band tension, overnight wear and the everyday habits that make a reading noisy. What you can control, and what you have to accept.
2 September 2026 · Setup guide
Why a personal median beats any published range, how many days you need before a trend means anything, and how to keep a baseline honest when life interrupts it.
2 September 2026 · Setup guide
A short, practical routine for a high reading — and an honest account of what slow breathing does, what it does not do, and why it changes the number mechanically.
2 September 2026 · Practice guide
If you have not read them yet, three explainers on the blog cover the reasoning these guides assume: what HRV actually measures — and what it doesn't, why you shouldn't compare your HRV to anyone else's, and how to read a stress score against your own baseline.
Not medical advice. Calmline is a consumer wellness app. It does not diagnose, treat, prevent or predict any condition, and nothing in these guides is a substitute for talking to a clinician about a health concern.
Calmline reads HRV on Apple Watch and scores it against the median of your own recent history — on-device, with no account and no server. It isn't on the App Store yet; the waitlist is the way in.
Calmline