Most health apps show today's steps and last night's sleep. CalmTide reads the Apple Health data you already have — sleep, HRV, workouts, resting heart rate, mindful minutes — and estimates what they add up to: an HPA Balance Score today and a weekly balance trend over 8 weeks, with every number showing what it's estimated from. It estimates stress load; it does not measure cortisol. Built entirely on your device.
CalmTide reads the metrics your Apple Watch already collects, weighs them with a named, citation-backed model, and turns them into a single weekly HPA Balance Score — plus a daily estimate of whether today's load is likely low, moderate, elevated, or high, and how much data sits under it.
HRV (SDNN) is a non-invasive signal of autonomic balance, read against your own baseline. CalmTide uses the readings taken while you sleep, and a sustained drop below your usual nudges your estimated load up.
How long you slept, how regular your timing is, and how continuous the night was. Since 1.6, a steady wake time counts toward the sleep component — and a night your watch didn't record leaves a gap, never a bad score.
Easy aerobic work and stacked hard sessions pull in different directions. CalmTide labels every workout with heart-rate data as reducing, neutral, or spiking for its estimated load — a session without heart rate claims no intensity — with acute-to-chronic ratio, monotony and strain as plain figures in your workout history on Pro.
CalmTide credits your mindful minutes from Apple Health, and its Breathe tab guides cyclic sighing and resonance breathing in 2, 5 or 10-minute sessions — free, and on your wrist too. Pro adds NSDR, a cold finish and a post-meal walk.
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.
Light in the window after you wake helps anchor your morning rhythm. Connect SolGlow and its morning-sun data feeds straight into that component of your score.
Your live HPA Balance Score ring with today's load estimate against your usual, 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 a breathing session.
Opens with a weekly HPA-balance hero, then reads your MET-minutes and zone distribution against both a 530 MET-minute weekly target and your own 8-week norm — with a week-over-week delta. A session list badges the cortisol effect of every workout with heart-rate data — reducing, neutral, or spiking — so you can see exactly which sessions helped and which cost you; sessions without heart rate are counted for dose but marked "intensity not measured".
The long view: your weekly HPA balance over 8 weeks, with life events — illness, travel, deadlines — pinned to it so shifts make sense, and a 7-day forecast of your load estimate. Weeks CalmTide couldn't measure are shown as gaps, not guesses. The full eight weeks, plus extended 60- and 90-day history, come with Pro.
Plus an Insights tab — with personalized benchmarks (Pro) that place your HRV and resting heart rate against normative ranges for your age and sex, plus cards for blood oxygen (SpO₂), walking heart rate, and time on your feet, a personal-average line 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 fitness signal.
CalmTide 2.0 gives breathing a tab of its own that you can follow with your eyes closed, puts your balance and readiness on the watch face, and finishes the work 1.6 started: the Trend now shows your weekly HPA balance, and every estimate counts only the days CalmTide actually measured.
Cyclic sighing (Balban 2023) and resonance breathing (Shaffer 2020) get their own home, in 2, 5 or 10-minute sessions, with a suggestion for the moment you're in and your mindful minutes this week — no target, no streak to keep. Free. The NSDR, cold-finish and post-meal-walk practices sit alongside on Pro.
A gentle haptic tap marks each breath, the screen stays awake for the session only, and with Reduce Motion on a pacer bar replaces the orb.
Two complications — CalmTide balance and CalmTide readiness — each showing when it last updated, so an old number never passes for today's. Scores on the wrist are Pro. On Apple Watch Series 9 and later, Double Tap starts and finishes a breathing session.
The Trend now shows your weekly HPA balance over 8 weeks, with your life events pinned to it; the arbitrary-unit cortisol number is retired. “Above your usual” and the forecast count only days CalmTide actually measured, and readiness waits for 7 nights of resting heart rate. Some scores rise, some fall — nothing about your body changed.
Confirm your age once for age-adjusted HRV and resting-heart-rate ranges. Until you do, CalmTide assumes 35 and says so — without calling you above or below a range. No Apple Watch yet? CalmTide now says plainly when it hasn't found sleep, HRV or resting heart rate, and what still works without them.
We re-read every paper CalmTide cites. Wrong authors are corrected, overstated findings are rewritten, and claims we couldn't source are gone. Fixed HRV “target” lines are removed, and CalmTide's own targets are labelled as its own on Methodology.
Also in 2.0: a one-time “New pattern found” note when your check-ins first show a pattern (an association, never a cause), the report renamed an appointment summary (Pro), clearer VoiceOver descriptions on every chart, and offer codes from the paywall or Settings. CalmTide 2.0 requires iOS 26 and watchOS 26. Full release notes →
Version 1.7 keeps the 1.6 promise and pushes it into the corners 1.6 missed: a workout without heart-rate data is no longer scored as the easiest kind of training, training load is shown as figures instead of a verdict, and the daily check-in gains an optional drink count. And the Apple Watch app stops being a mirror: your balance on the watch face, haptic-paced breathing on the wrist, and a breathing session one tap away in Control Centre, on the Action Button, or by asking Siri.
A manually logged session, a third-party app that saves duration only, or a day the watch stayed home used to be credited as easy Zone 2 — the most favourable kind of training in the model. Those minutes still count toward your weekly dose, worked out from calories and capped so an unmeasured session can never out-score a measured one, but they claim no zone and no cortisol direction, and the Week tab tells you how many minutes came through without heart rate.
The acute-to-chronic card no longer files you under a coloured band. The paper behind those bands measured injuries in team-sport athletes, not stress hormones, so the card now shows your last 7 days against your 4-week base, a single reference mark at 1.0×, and monotony and strain as plain numbers. With no 4-week base to compare against it says so, instead of calling you optimal. Still Pro, still on the Week tab.
Tag a night with alcohol and a small stepper appears; leave it blank and the night is a normal alcohol night. Once you have enough nights on each side, Insights compares your own next-day resting heart rate and HRV after one drink against two or more — your numbers, both sample sizes shown, no score and no lecture. Nights without a count are left out, not assumed light. Nothing is read from or written to Health for this.
The Today card that draws the daily cortisol curve is now titled “The typical cortisol rhythm” — a population model, anchored to your wake time when your watch recorded one. When it didn't, the curve is education only: no invented wake time, no “you are here” marker, and nothing to scrub a clock time off.
Breathwork descriptions now say what the cited study measured — cardiac vagal activity, during the session — rather than promising to lower cortisol. Morning-light and sleep-timing tips describe how your body clock times the morning cortisol rise instead of promising to sharpen it. And the environmental-sound card no longer draws a “safe” line that the WHO guideline it cited never set for stress.
Your balance now lives on the watch face and in the Smart Stack as a complication, refreshed in the background rather than only when you open the iPhone app. Breathe on the wrist with a haptic at every phase change — cyclic sighing or resonance breathing, the same timings as the phone — and the session is credited to Mindful Minutes through your iPhone, with no new Health permission on either device. A second watch page shows the three measured signals behind the score. Complications and scores on the wrist are Pro; breathwork is not.
Start a breathing session from Control Centre, the Action Button, or by asking Siri — “Start breathing in CalmTide” — without hunting for the app. Same sessions, same credit to Mindful Minutes, and never paywalled.
Two Home Screen widget check-ins on consecutive days without opening the app used to overwrite each other, breaking a streak through no fault of yours. The pending taps are now a queue, drained oldest-first, so both days are kept.
Released 10 September 2026 with no new Health permissions. The 1.6 changes it builds on are described below.
A stress score is only worth the measurements under it. Version 1.6 tightens those: HRV read from the night you actually slept rather than a 24-hour average that mixed in your commute, sleep scored on regularity as well as hours, and a rule that runs through the whole app — anything CalmTide couldn't see leaves a gap in the picture, never a zero in your score.
Your daily HRV is now the average of the SDNN readings taken inside the night's sleep — not a calendar-day mean that folded in your commute and your workout. On a night the watch wasn't worn, CalmTide falls back to the day's readings and labels the number as an all-day average, rather than quietly changing what it means. Scoring and baselines use only the overnight figure, so a fallback night sits out a comparison instead of being compared against nights measured a different way.
How consistent your sleep timing is predicts more than how long you slept, so a steady wake time now counts toward your score — the Sleep Regularity Index takes 30% of the sleep component, split off the existing duration terms rather than piled on top. Under three nights of sleep timing leaves it unmeasured and renormalises the rest.
Awakenings, time awake in bed, and sleep efficiency — for the nights your sleep source actually records them. Nights without that detail are left out of the averages rather than counted as perfect.
The gap between the body clock you keep on work days and the one you keep on free days, measured from your mid-sleep point the way the chronobiology literature defines it. It needs at least two free nights and three work nights, and reports nothing below that.
It was never a measured cortisol awakening response, and it no longer claims to be. The number is a proxy blended from your wake time, your morning light and your sleep quality — which is what it always was. The trend milestone that predicted a mental-health outcome from that proxy is gone, and the sleep-regularity research note now states the mechanism instead of quoting depression, anxiety and mortality figures.
No daylight sensor, too few nights of sleep timing, a night the watch was charging — those now leave a gap in the picture instead of a zero in your score. Morning light is also counted in the window after you wake rather than across the whole day, so an evening walk no longer ticks a morning box.
1.6 asks for no new Health permissions. The read set shrank by one type — exercise time was being requested and never used — and nothing was added.
Your scores always raised the same question: what, specifically, is doing this? Version 1.5 answers it from your own data — patterns read the morning after, when the biology actually lands, a weekly retrospective that ranks exactly what moved your score in points, and a Practice hub with the right dose for the moment you're in. Compared across your own days, and never presented as cause and effect.
See what caffeine, alcohol, late meals and hard workouts did to your HRV, sleep and readiness the next morning — when the biology actually lands. Plus the habit your load estimate moves with most, drawn from your own data — suggestive, never causal.
After a few weeks of check-ins, see whether how you feel actually lines up with your sleep, HRV and training. It waits until it has enough days on both sides of a comparison before it says anything.
A weekly retrospective that ranks exactly what moved your score, in points — sleep, morning light, HRV, mindfulness, training load — this week against last.
Cyclic sighing and resonance breathing in 2, 5 or 10-minute doses, with a suggestion for the moment you're in: evening wind-down, post-workout reset, elevated load.
Log how you feel straight from the Apple Watch app — it lands on your phone through the same path as the Home Screen check-in widget, so your streak and your day stay in one place.
Tell CalmTide what you're working on — stress, sleep, or training balance — and today's recommendations reorder around it instead of treating every goal the same.
Your daily check-in can mirror to Apple Health as that day's State of Mind entry, and a mood you logged in Health fills in a check-in you missed. Optional, your own entry only, and it asks the first time you check in.
If you log caffeine to Apple Health, see what an after-2pm dose tends to do to the next morning's HRV — compared against your own earlier-cutoff days, and phrased as an association.
Export a full backup and restore it on any device from Profile → Your Data. Personal records for your longest streak, best HPA week and calmest morning. Calm Coach now leads with today's status, readiness and last night's sleep. Today reorders by time of day, notification taps open the screen they're about, and dozens of reliability fixes.
CalmTide writes exactly two things to Apple Health, both entered by you: a completed breathwork or resonance session, saved as Mindful Minutes, and — new in 1.5, optional — your own daily check-in, mirrored as that day's State of Mind mood. Everything else it reads stays read-only, 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: estimated stress 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 data feeds the morning-rhythm component of 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.
Two watch-face complications — CalmTide balance and readiness, each showing when it last updated — haptic-paced breathing with your live heart rate, check-ins that sync back to your iPhone, and Double Tap on Series 9 and later. Scores on the wrist are Pro; breathing never is.
A Today-summary and HPA-ring widget for your Home Screen, plus circular, rectangular, and inline Lock Screen widgets — your trend one glance away.
A morning check-in that arrives around your usual wake time, post-hard-workout recovery nudges, a Sunday weekly summary, and an alert when two hard sessions stack up. Tapping one now opens the screen it's about — a wind-down cue opens the wind-down session.
Everything is computed on-device from Apple Health. No account, no analytics, and no health data ever leaves your phone.
One Apple Health sheet on first run lists every type CalmTide can read, and each is yours to allow or skip — scores work with whatever you share. Apple Health's State of Mind has its own prompt, shown the first time you check in.
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 model is informed by published research on exercise, sleep, breathing and the HPA axis. For 2.0 we re-read every paper the app cites against what it actually found: wrong authors were corrected, overstated claims rewritten, and anything we couldn't source removed. The full list lives on the Sources sheet in the app; a few starting points are below.
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 every day. CalmTide Pro adds your weekly HPA balance over 8 weeks, extended 60- and 90-day history, a 7-day forecast of your load estimate, score & forecast widgets, scores on Apple Watch, the practice library, the appointment summary, training load as plain figures — acute-to-chronic ratio, monotony and strain — and Calm Coach, the optional on-device explainer. Pro also opens the weekly retrospective, what your check-ins reveal, and caffeine timing.
Billed monthly, renews until you cancel. No free trial on the monthly plan.
Billed yearly, renews until you cancel. New subscribers get a 1-month free trial first.
A one-time purchase. Never renews, never expires — yours for good.
Every plan unlocks the same Pro features
The HPA Balance Score and today's load estimate, one smart recommendation, the daily protocol and five-second check-in, the Breathe tab with guided cyclic-sighing and resonance sessions, morning-after patterns, personal records, quiet notifications — and a data-confidence indicator on every score, so you always know how much data sits under the number. Your data stays yours: export a full backup or restore it any time.
Subscriptions auto-renew until cancelled, and you can cancel any time in your Apple ID settings. The annual plan includes a 1-month free trial for new subscribers; the price and any trial are shown before you confirm. No account required. Requires iOS 26 or later; an Apple Watch on watchOS 26 or later is recommended — scores need it, or another app that writes sleep, HRV or resting heart rate to Apple Health. See the Privacy Policy and Terms of Use.
Now on version 2.0. See the update history →