Most health apps show today's steps and last night's sleep. CalmTide shows the cumulative biological outcome of those behaviours — your estimated baseline cortisol and HPA-axis balance — as a trend you can actually move over 8 to 12 weeks. Built entirely from Apple Health, on your device.
CalmTide reads the metrics your Apple Watch already collects, weighs them against published exercise-and-cortisol research, and turns them into a single weekly HPA Balance Score — plus a daily read on whether today's cortisol is likely low, moderate, elevated, or high.
HRV (SDNN) is the single best non-invasive proxy for HPA-axis state. CalmTide tracks your rolling average — every drop nudges your estimated cortisol load up.
Deep-sleep shortfall and REM disruption raise next-day cortisol. CalmTide reads your sleep stages and weights deep sleep most heavily.
Zone 2 lowers baseline cortisol; stacked Zone 4–5 sessions spike it. CalmTide classifies every workout and flags overtraining before it costs you.
As little as five minutes a day has a measurable cortisol effect. CalmTide credits logged mindful minutes and includes two guided sessions — a cyclic-sighing exercise and a resonance-breathing pacer.
Resting and walking heart rate, respiratory rate, blood oxygen (SpO₂) and VO₂ max round out the picture as secondary stress and recovery signals — each now viewable on its own Insights card.
Morning light sharpens your Cortisol Awakening Response. Connect SolGlow and its sun & CAR data feed straight into your score.
Your live HPA Balance Score ring with a cortisol-vs-baseline read, one smart recommendation, a five-second daily check-in, and a daily protocol checklist topped by a “days on track” consistency strip. Recovery tiles now lead with how far each signal sits from your own baseline (“above usual · +12%”), and a tap starts the new resonance-breathing session.
Opens with a weekly HPA-balance hero, then reads your MET-minutes and zone distribution against both the research-backed 530/week target and your own 8-week norm — with a week-over-week delta. A session list badges every workout's cortisol effect — reducing, neutral, or spiking — so you can see exactly which sessions helped and which cost you.
The headline view: an 8-week estimated baseline-cortisol line against an optimal target trajectory, with annotated spikes (that stacked-HIIT week shows up here) and milestone markers like "HRV improved" or "CAR score crossed 70." This is the anxiety-relevant signal most apps never show you.
Plus an Insights tab — now with personalized benchmarks that place your HRV and resting heart rate against typical ranges for your age and sex, new cards for blood oxygen (SpO₂), walking heart rate, and time on your feet, a personal-average line and a healthy-range band on your charts, and your tagged days turned into at-a-glance comparison bars — alongside HRV history, sleep-architecture breakdowns, a sun-to-next-day-HRV correlation, noise-exposure trends, and VO₂ max as a long-term HPA-health proxy.
Version 1.4 gives your practice credit. Morning light coaching helps you anchor your cortisol awakening rhythm by catching outdoor light soon after you wake, life events pin illness, travel, or a big deadline onto your 8-week baseline so a shift makes sense instead of feeling random, and breathwork now counts — completed sessions save to Apple Health as Mindful Minutes.
Anchor your cortisol awakening rhythm by catching outdoor light soon after you wake — with a two-week “circadian anchor” score in Insights, and a clearer “morning light → next-day HRV” insight.
Pin illness, travel, or a big deadline onto your 8-week baseline — so when the line moves, you can see why, instead of a shift feeling random.
The morning check-in now arrives around your usual wake time, a heads-up lands the evening before a predicted high-cortisol day, and a wind-down cue follows a late hard session. Plus a one-tap check-in widget for your Home Screen.
Completed breathwork and resonance sessions now save to Apple Health as Mindful Minutes — the one thing CalmTide writes, still entirely on your device. Estimates remain wellness context, not a diagnosis.
SolGlow owns the sun: UV, vitamin D, and morning-light timing. CalmTide owns stress recovery: cortisol load and HPA-axis balance. Install both and they share a secure on-device container — no servers, no accounts — so each app gets smarter. Neither needs the other to work.
When SolGlow is connected, your morning-sun and CAR data feed CalmTide's weekly score, and a new "Sun → next-day HRV" correlation appears in Insights — so you can see, in your own data, whether getting out in the morning actually steadies your nervous system.
Your HPA score and today's recommendation on your wrist, synced from the phone.
A Today-summary and HPA-ring widget for your Home Screen, plus circular, rectangular, and inline Lock Screen widgets — your trend one glance away.
An 8am check-in, post-hard-workout recovery nudges, a Sunday weekly summary, and an alert when two hard sessions stack up.
Everything is computed on-device from Apple Health. No account, no analytics, and no health data ever leaves your phone.
CalmTide asks for the essentials on day one and requests deeper metrics only when you explore the features that use them.
Scores are clearly labelled as estimates from published research — not a clinical cortisol measurement. CalmTide tells you what it can and can't know.
CalmTide's scoring models are informed by published research on exercise, recovery, and the HPA axis — including the dose-response relationship between training volume and cortisol, and the measurable cortisol effects of sleep, breathwork, and morning light.
CalmTide provides wellness estimates based on published exercise-physiology research. It is not a medical device and should not be used to diagnose or treat any condition. Read the deep dive on the science behind CalmTide.
Free to download and use. CalmTide Pro unlocks the deeper Insights, full history, the cortisol forecast, personalized benchmarks, Home Screen & Lock Screen widgets, and the Apple Watch app — $4.99/month or $29.99/year, each with a 1-month free trial, or a one-time $19.99 lifetime unlock. No account required. Requires iOS 18.6 or later; Apple Watch (watchOS 11+) recommended.
Now on version 1.4 — “Daily rhythm.” See the update history →