What HP is
HP shows your energy as a game’s health bar. Sleep and meals bring it back; being awake, moving and conditions spend it. The surface stays simple. This page is where the inside is open.
One day
Overnight the bar fills while you sleep. Through the day it falls, and each meal adds back a little at a time as it digests.
How HP is spent
Drain is how fast HP is falling right now, shown on Home as HP per hour.
- Being alive costs HP all day. It comes from your resting metabolic rate and changes with the time of day.
- Moving costs more. It comes from active energy in Apple Health, weighted by how hard the effort was.
- Conditions multiply the drain (see Conditions). Fever, feeling unwell and a hangover also add a small steady cost.
- HP is scaled to your own average day, so the same bar means the same thing for someone very active and someone who is not.
- The fuller the bar, the faster it spends; the emptier, the more the body economises. Above half a bar, drain rises from ×1 at half to ×3.5 at full. Below half it eases, down to ×0.80 near empty. Asleep, only the easing side applies.
- HP does not go below 3% of your maximum. Anything spent past that is carried as debt, up to 25% of your maximum.
How sleep brings it back
Sleep recovery = maximum HP × 0.65 × duration × quality × disruption × condition
| Sleep | 3 h | 4 h | 5 h | 6 h | 7–9 h | 10 h | 12 h |
|---|---|---|---|---|---|---|---|
| Duration factor | 0.40 | 0.55 | 0.70 | 0.85 | 1.35 | ≈1.31 | ≈1.26 |
Between 6 and 7 hours it rises in a straight line.
- Quality: deep sleep 35%, REM 25%, waking in the night 25%, heart-rate variability 15%. Without sleep stages your morning answer is used (well 0.95, OK 0.85, not well 0.70); with neither, 0.88. Range 0.4–1.05.
- Disruptions: alcohol before bed, a meal within 2 hours of bed (×0.96), caffeine in the 6 hours before. Range 0.5–1.0.
- One night can bring back at most 73% of your maximum. This limits one night’s recovery, not the bar.
- Recovery arrives evenly, minute by minute, while you sleep. The main sleep is the longest sleep of 3 hours or more for each day you wake up.
- Debt is settled at the main sleep. Recovery first repays debt, then fills the bar. When the main sleep begins, any debt still left is cleared; HP does not move. Naps do not clear it.
How meals bring it back
Meal recovery = maximum HP × (0.35 ÷ 3) × quality × amount × match × condition
- It arrives as the meal digests. An ordinary meal is about 90% in by 90 minutes; a meal rich in fat and protein, or a larger one, takes longer.
- Plates within 60 minutes of the one before are counted as one meal (12:17, 12:40 and 13:03 are one lunch), so splitting one lunch across several photos does not multiply its recovery.
- Quality: macronutrients 40%, micronutrients 25%, food quality 35%.
- Amount: the longer since your last meal, the more one meal can count.
- Match: when a meal has what the moment needs — vitamin C and fluids with a fever, for example — it counts for more, up to ×1.30. A meal that doesn’t match never counts for less.
- Everything digesting at once is capped at 40% of your maximum.
- The meal result shows +N HP: what this meal will add.
How meals are read
- Photos are HP Pro; typing is free. Each has its own consent, and nothing is sent until you agree.
- Both go through HP’s relay to OpenAI. No health records or account details are attached.
- For packaged foods and shop items, the reading may search the web once, by product name, for the maker’s published values.
- kcal is the value the reading returned, or the maker’s published value when it was found.
- Each line says where its numbers came from: Rough estimate (the reading’s estimate), Official value (the maker’s published values, found by the search), Food composition table (when you choose a food from the list).
- Any line can be fixed with a tap: the amount, a different food, or “this wasn’t in it”. Recovery updates straight away.
- kcal is shown on the meal result, in today’s meals and in the day’s ledger. There is no daily kcal total, and HP never warns you about eating too much.
- Japan’s food composition table is still used when you swap a line for a food from the list, and when you log from the drinks shelf.1 Those lines also carry vitamin D, folate and calcium (HP’s common daily reference: 9 µg, 240 µg, 650 mg — not a personal recommendation); meals read from a photo or text do not.
- Drinks: pure alcohol in grams = volume (ml) × strength (%) ÷ 100 × 0.8. Caffeine uses what you enter or the product’s figure; an unknown amount stays unknown, never zero.
1 Standard Tables of Food Composition in Japan 2020 (Eighth Revised Edition), Ministry of Education, Culture, Sports, Science and Technology. Spelling normalisation and unit conversion by HP.
The water tank
- Your daily water target is body weight × 0.025 L (1.2–2.2 L), plus 0.08 L for each degree above 25 °C (up to +0.8 L), never more than 3.0 L.
- Water is counted as a tank that drains through the day. It holds 4 hours of your target, and can store up to twice that as reserve; the gauge stays full above 4 hours.
- During the main sleep it drains at one third of the daytime rate.
- Empty for 2 hours means Dehydrated. Being empty alone is not. Any water that lifts the level above empty ends it.
- No water recorded for 24 hours shows “?” and never raises Dehydrated — not recording is not being dry.
- The tank does not reset at midnight; it is replayed from the last 72 hours of records.
Conditions
Conditions are how HP says “something about today is different”. They are HP’s own coefficients, not measured medical effects.
| Condition | Effect | When it appears | When it clears |
|---|---|---|---|
| Dehydrated | Drain ×1.1 | The water tank has been empty for 2 hours | Drinking water |
| Seated | Drain ×1.15 | More than 120 minutes without standing | Standing for 3 minutes |
| Fever | Drain ×1.3, recovery ×0.9, plus a steady cost | You report it | “Better”, or it fades within a day |
| Unwell | Drain ×1.2, plus a steady cost | You report it (headache, stomach, feeling off…) | “Better”, or it fades within a day |
| Hangover | Drain ×1.2–1.5, plus a steady cost | Drinks before waking went past your own tolerance | It wears off during the day |
| Strained | Drain ×1.1–1.35 | You report it, or answer “Strained?” | “Better”, or it fades within a day |
| Heat / Cold | Drain ×1.1–1.25 | An outdoor workout at 28 °C or more / 5 °C or less; or you report it | The workout ends |
| Fatigue | Maximum HP −3 to −12% | 3 of the last 5 nights under 6 hours, or 4 days ending below half | Rested nights and days that don’t end low |
| Cycle | Recovery ×0.95–0.85, maximum HP −2 to −8% | Only if you turn cycle tracking on: a period recorded in Health, or you report it | Recorded in Health: 12 hours after the entry. Reported: at the end of that day, or when you undo it |
| Follicular / Mid-cycle / Luteal | ×1 → 0.95 / none / ×1.05–1.10 | Estimated from your recorded cycles (median of the last 3; 28 days by default) | The estimated phase changes |
| Caffeinated ▲ → Rebound | ×0.85 for 210 min, then ×1.15 for 240 min | Coffee or an energy drink | Time |
| Rested ▲ | ×0.9 | Last night 7 hours or more, and good quality | Checked each day |
| After exercise ▲ | ×0.9 | 30 minutes or more of exercise yesterday, and a resting heart rate at or below yours this morning | Checked each day |
| Steady rhythm ▲ | ×0.9 | Today’s heart-rate variability 10% or more above yours | Checked each day |
| Resting ▲ | ×0.85 | Awake, not moving, heart rate at or below yours, for more than 30 minutes | When the rest ends |
| Mending ▲ | Recovery ×1.2 | 3 days after a reported fever ends | After the 3 days |
| Unwell? / Strained? | none | Wrist temperature, resting heart rate and HRV all off together / HRV 20% or more below yours | When the readings settle; answering makes it a real condition |
▲ = a buff. Buffs together go no lower than ×0.8; drain effects multiply and stop at ×2.2; recovery factors stay between 0.5 and 1.4; maximum HP drops by 25% at most. During the main sleep, Dehydrated and Seated are paused. Cycle and its phases are shown only if you turn them on, and not during pregnancy; the estimate can’t be used to confirm ovulation or for contraception.
Maximum HP and the five stats
Your maximum HP comes from cardio fitness (VO₂max), muscle (fat-free mass index) and recovery (sleep and heart-rate variability). It is re-evaluated each day and moves no more than 2% from the day before; if an input is missing, it waits.
The five stats are measured against published norms where they exist, and HP’s own documented scales where they don’t:
- Stamina — VO₂max against age-and-sex norms from the FRIEND registry (published).
- Strength — fat-free mass index, with the Kouri height correction, placed on a distribution centred on Kelly (2009, DXA): an approximation built from published figures. It measures muscle mass, not strength per kilogram.
- Recovery — sleep duration and efficiency against published guidance; resting heart rate against HP’s own bands.
- Resilience — half is heart-rate variability against 5-minute age norms (Voss, published); the other half is how regular your bedtime is and how little you wake in the night, on HP’s own scales. HP can’t see stress from outside your body, so it scores the signs that show up in your body: the fewer, the higher.
- HP — the level of your maximum HP itself.
Your rank moves from F to S as they grow. Each stat keeps the date it was measured; a line carrying an earlier value forward is dotted. Past days are never re-scored with today’s scale.
Reading the sleep screen
A night’s recovery score uses the same calculation as the Recovery stat: sleep duration 50%, efficiency 25%, resting heart rate 25%, reweighted when something is missing. The stage band is drawn from the recorded timeline; nothing is invented from a total.
The five letters on the sleep screen are HP’s own display scale:
| Scores 100 | Scores 0 | |
|---|---|---|
| Duration | 7–9 hours | 2 hours outside that band |
| Deep sleep | 13–23% of the night | 13 points outside |
| REM | 20–25% | 20 points outside |
| Efficiency | 95% (85% is 80) | 75% |
| Waking in the night | 20 minutes or less | 80 minutes or more |
Between the two, the score moves in a straight line.
| S | A | B | C | D | E | F |
|---|---|---|---|---|---|---|
| 95+ | 80+ | 60+ | 40+ | 20+ | 5+ | below 5 |
Night readings. For resting heart rate, heart-rate variability, wrist temperature, respiratory rate and blood oxygen, the screen shows that night’s average next to the same source’s average over the 14 days before bedtime. Unmeasured is “—”.
Estimated or self-reported nights get no stage letters. This is not a medical standard, and it does not mean sleep beyond 9 hours is unnecessary. References: AASM/SRS adult sleep-duration consensus (2015); NSF sleep-quality indicators (2017). The deep-sleep and REM bands and the letter conversion are HP’s product decisions.
Mental stability
Mental stability on Home’s condition gauge is HP’s estimate of how much your heart-rate variability (SDNN, from the last 24 hours) sits at or above your own usual level, compared with the same source’s previous 14 days. It needs at least 7 days to have a baseline. It is not a measure of feelings, and exercise, sleep and illness move it too.
The same HRV is used three ways: Resilience compares it with age norms, mental stability with your own usual, and “Strained?” appears when it is 20% or more below your usual.
The day’s ledger
Each day closes as a ledger. SPENT lists being alive, moving, conditions and what was held at the floor; RECOVERED lists sleep, each meal and debt repaid. Debt settled at the main sleep is shown outside both totals. Meals show their thumbnail, name, kcal and time.
Free and Pro
Everything is free for the last 31 calendar days, including today: HP, conditions, water, typed and manual meals, trends, the daily ledger and monthly summaries. HP Pro adds meals by photo, and takes trends, the daily ledger and monthly summaries back past 31 days. Pro never changes how HP is calculated. More about HP Pro
Your records
HP works without an account. With optional Sign in with Apple you can save your records to HP’s own storage and restore them on another device; signing in alone uploads nothing. Privacy policy
For reviewers
HP is an independent wellbeing model; scores and coefficients are not clinical measurements. Missing data stays missing. HP’s calculations run on the device. Meal reading — photos with HP Pro and separate consent, typed text with its own consent — goes through HP’s relay to OpenAI, with no health data attached. Account Save/Restore is optional and explicit. Pro changes convenience and the history window, never the calculation.