How Today's Workout calculates your readiness score

The seven axes

Each input is placed on its own 0–100 curve. The curves are informed by the reference ranges listed below. The weights, the points between the reference values and the sleep cap are product rules, and the combined score is not a clinically validated measure of recovery.

Axis	Weight	100 points	0 points	Reference
Sleep duration	0.30	7–9 hours	no sleep	NSF 2015 recommendation, AASM/SRS consensus of at least 7 h; long sleep over 10 h scores lower (Cappuccio 2010)
Sleep efficiency	0.10	85 % or more	30 % or less	Ohayon 2017 (NSF sleep quality indicators)
Weekly aerobic minutes (last 7 days)	0.20	300 min	0 min	WHO 2020: 150 min is the pass line (60 points), 300 min is full; more than 300 is not penalised (Arem 2015)
Weekly strength days (last 7 days)	0.10	2 days or more	0 days	WHO 2020: strength training on 2 or more days a week (1 day = 50 points)
Resting heart rate	0.15	55 bpm or lower	110 bpm	Zhang 2016 meta-analysis: each 10 bpm increase raises all-cause mortality risk by about 9 %; 100 bpm is the clinical tachycardia threshold
Heart rate variability (7-day rolling)	0.10	42 ms or higher	0 ms	Nunan 2010: healthy-adult mean rMSSD 42 ms; higher values are never penalised because individual variation is large
Overnight respiratory rate	0.05	12–20 breaths/min	6 or 32 breaths/min	Clinical convention, not a specific study

Steps count toward the aerobic axis. A daily average of 8,000 steps is treated as the 150-minute pass line and 12,000 steps as the 300-minute target (Saint-Maurice 2020, Paluch 2022); 2,000 steps or fewer add nothing. The app takes the larger of logged workout minutes and step-derived minutes, never the sum, so a walk you also logged as a workout is not counted twice.

If you tell the app about a life stage that has its own WHO activity guideline, such as pregnancy, the aerobic curve follows that guideline. This can only prevent a penalty; it never scores you lower than the default curve.

How the axes become one score

1. Weighted average. The seven axis scores are combined with the weights above. Sleep (duration plus efficiency) is 40 % of the score, activity 30 %, resting heart rate 15 %, HRV 10 %, respiratory rate 5 %.
2. Missing data is skipped, not zeroed. If an axis has no data, its weight is removed and the others are re-normalised. A night without the watch is treated as unknown, not as a bad night.
3. Lifestyle adjustment. If you log alcohol, evening caffeine, mindfulness, a short nap, or the app sees blood pressure, glucose or breathing disturbances above your own baseline, a small adjustment is added. The total adjustment is clamped to between −10 and +3 points, so measured physiology always outweighs inferred context. Days with no lifestyle records get exactly 0.
4. Clamp to 0–100.
5. Sleep cap. Last of all, the score cannot exceed the sleep-duration axis score plus 22 points. After five hours of sleep the sleep axis is 30, so the whole score is capped at 52 no matter how good everything else looks. If sleep was not recorded, no cap is applied. Because the cap comes last, no other step can lift a score above it.

The five condition levels

Score	Level	Meaning in the app
85–100	5	Peak day
70–84	4	Good day
55–69	3	A normal day
40–54	2	Lower the intensity
0–39	1	Rest day

The level starts from this table. A separate layer that reads additional overnight signals can then move the level shown by at most one step in total. It never changes the 0–100 score, and the app explains the move when it happens.

When the app does not show a score

• Fewer than 7 days of history: no score is shown.
• 7–29 days: the score is shown with a "learning" label.
• No core data for last night (no sleep, resting heart rate or HRV): no score. Weekly activity alone is not enough, because it describes how you have been living, not how your body is today.

What the score is not

• It is not a comparison with your personal average. Earlier versions of the app (before scoring engine 1.0.0) used a personal baseline; the current engine does not. The "compared with your usual" figures on the briefing screen are shown for context only.
• A sudden jump in training load is shown as a warning card but is not part of the score.
• Reaching the daily step goal is celebrated but adds nothing to the score or level.
• The app is not a medical device and the score is not a diagnosis. It is wellness information for deciding how hard to train today.

Privacy

All score calculations run on the iPhone. The server stores:

• Account information (email, display language), only if you create an account. Every analysis feature works without one.
• Diagnostics, only if you turn diagnostic sharing on: app events, whose names and values come from a fixed list, and error reports, which carry the error type, the system's error message and a stack trace. You can delete them in Settings.
• A once-a-day "app opened" signal: a random install ID, the date, the platform and the app version. It is not linked to your account and contains no health data. You can delete the signals already sent in Settings; deleting the app stops them.

Sources

• Today's Workout on the App Store: https://apps.apple.com/kr/app/id6803109089
• In the app: Settings › How it's calculated, which lists the same reference points and their limits.

This article is general health information and is not a substitute for medical diagnosis or treatment. Consult a healthcare professional if you have concerns.