Every recovery, readiness or energy score starts from HRV and adds other signals, and no maker publishes how it combines them. This guide lists what each maker says goes into its score, in its own words, shows how HRV is set against a baseline Baseline Your own usual HRV level and range, built from weeks of readings taken the same way. Comparing a reading with your baseline says more than comparing it with other people. More about Baseline inside each one, and explains why two devices can read the same night and disagree.
Documentation checked: 14 October 2026. Makers revise their scores, so check the linked page for the current version.
Pick a score and see its inputs
What is in a readiness score?
From the makers' own documentation
- HRV : named by the maker HRV Balance: "How has my HRV changed over the past few weeks?" (a two-week average against three months).
- Resting heart rate : named by the maker Resting Heart Rate: "Was my RHR substantially higher or lower than usual?"
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Sleep, Sleep Balance, Sleep Regularity and Recovery Index (hours of sleep after the heart rate reached its low).
- Temperature : named by the maker Body Temperature: "Is my body temperature higher or substantially lower than usual?"
- Activity or load : named by the maker Previous Day Activity and Activity Balance (recent load).
Oura's Readiness Score names 5 of the six inputs: HRV, resting heart rate, sleep, temperature and activity or load. "The sum of these daily Readiness Contributors make up your Readiness Score." No weights are published.
- HRV : named by the maker Heart rate variability; the API field for it is named hrv_rmssd_milli.
- Resting heart rate : named by the maker Resting heart rate.
- Breathing rate : not named Not named by the maker.
- Sleep : not named Not named by the maker.
- Temperature : named by the maker Skin temperature, for WHOOP 4.0 and later.
- Activity or load : not named Not named by the maker.
Also: Blood oxygen (SpO2) on WHOOP 4.0 and later. Sleep and breathing rate are not named in the developer documentation.
WHOOP's Recovery names 3 of the six inputs: HRV, resting heart rate and temperature. WHOOP lists the measurements that "factored into the score" but not how they are combined.
- HRV : named by the maker HRV status (the seven-day average against your baseline range), and the stress history of the last 3 days, which itself comes from HRV.
- Resting heart rate : not named Not named by the maker.
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Last night’s sleep score and the sleep history of the last 3 nights.
- Temperature : not named Not named by the maker.
- Activity or load : named by the maker Acute load (recent training) and recovery time.
Garmin's Training Readiness names 3 of the six inputs: HRV, sleep and activity or load. The manual lists the six factors. It does not say how they are weighted.
- HRV : named by the maker Heart rate variability.
- Resting heart rate : not named Not named by the maker.
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Sleep quality: "Good sleep charges your Body Battery."
- Temperature : not named Not named by the maker.
- Activity or load : named by the maker Activity data: "Strenuous activity and high stress can cause your Body Battery to drain more quickly."
Also: Stress level, which Garmin derives from HRV while you are inactive. Food and caffeine have no effect.
Garmin's Body Battery names 3 of the six inputs: HRV, sleep and activity or load. The manual names the four inputs and nothing more.
- HRV : named by the maker "Your device analyzes your heart rate variability while you are inactive to determine your overall stress."
- Resting heart rate : not named Not named by the maker.
- Breathing rate : not named Not named by the maker.
- Sleep : not named Not named by the maker.
- Temperature : not named Not named by the maker.
- Activity or load : not named Not named by the maker.
Garmin's Stress level is HRV only: a rescaled HRV number, not a mix. HRV is the only named input. How it maps to 0–100 is not published.
Source: Heart Rate Variability and Stress Level (Garmin owner’s manual)
- HRV : named by the maker Heart rate variability (RMSSD) from roughly the first four hours of sleep.
- Resting heart rate : named by the maker Heart rate over the same window: "Heart rate has the biggest influence when forming the score."
- Breathing rate : named by the maker Breathing rate, "the smallest" influence.
- Sleep : not named Not named by the maker.
- Temperature : not named Not named by the maker.
- Activity or load : not named Not named by the maker.
Also: A separate Sleep charge compares the sleep score with your usual level.
Polar's Nightly Recharge (ANS charge) names 3 of the six inputs: HRV, resting heart rate and breathing rate. Polar ranks the three inputs by influence but does not give the weights.
Source: Nightly Recharge recovery measurement (Polar Support)
- HRV : named by the maker Heart rate variability.
- Resting heart rate : named by the maker Resting heart rate.
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Sleep.
- Temperature : not named Not named by the maker.
- Activity or load : not named Not named by the maker.
Also: Activity was an input in the earlier version and is not in the updated algorithm.
Fitbit's Daily Readiness Score names 3 of the six inputs: HRV, resting heart rate and sleep. Google names the three inputs and does not publish the formula.
- HRV : named by the maker Heart rate variability.
- Resting heart rate : named by the maker Sleeping heart rate.
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Sleep time average, sleep time consistency, bed and wake time consistency, and sleep timing.
- Temperature : not named Not named by the maker.
- Activity or load : named by the maker Previous day activity.
Samsung's Energy Score names 4 of the six inputs: HRV, resting heart rate, sleep and activity or load. Samsung lists the metrics the score combines and nothing about their weights.
- HRV : named by the maker HRV Form: your HRV baseline and how far last night departs from it; also the Stress Rhythm Score, which tracks heart rate and HRV across the day.
- Resting heart rate : named by the maker Overnight resting heart rate against your own baseline.
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Sleep Index: length, efficiency, stage split and timing.
- Temperature : named by the maker Skin temperature against your usual overnight level.
- Activity or load : not named Not named by the maker.
Ultrahuman's Recovery Score names 4 of the six inputs: HRV, resting heart rate, sleep and temperature. "Each is graded on its own; then the five combine into the 0 to 100 score." No weights are published.
Source: Recovery Score (Ultrahuman)
- HRV : named by the maker Vitals, including Recovery HRV analysed against your personal baseline.
- Resting heart rate : not named Not named by the maker.
- Breathing rate : not named Not named by the maker.
- Sleep : named by the maker Sleep score.
- Temperature : not named Not named by the maker.
- Activity or load : named by the maker Recent activity and training load.
Also: Vitals also cover heart rate, breathing rate and wrist temperature; Apple does not say how each counts.
Apple's Readiness names 3 of the six inputs: HRV, sleep and activity or load. Apple names four inputs and publishes no formula. It has not said which statistic Recovery HRV uses.
- HRV : named by the maker RMSSD from a chest strap or finger sensor reading, with "a natural log (ln) applied".
- Resting heart rate : not named Not named by the maker.
- Breathing rate : not named Not named by the maker.
- Sleep : not named Not named by the maker.
- Temperature : not named Not named by the maker.
- Activity or load : not named Not named by the maker.
Elite HRV's HRV Score is HRV only: a rescaled HRV number, not a mix. The score is a rescaled ln(RMSSD), set so that "everyone fits in a 0 to 100 range" using over 6 million readings. The exact mapping is not given.
- HRV : named by the maker "Calculated from lnRMSSD."
- Resting heart rate : not named Not named by the maker.
- Breathing rate : not named Not named by the maker.
- Sleep : not named Not named by the maker.
- Temperature : not named Not named by the maker.
- Activity or load : not named Not named by the maker.
Welltory's HRV Score is HRV only: a rescaled HRV number, not a mix. Welltory names lnRMSSD as the input and publishes no formula or thresholds.
With JavaScript off, every score is listed below the menu.
A list of scores, one per device, with six inputs for each: HRV, resting heart rate, breathing rate, sleep, temperature and activity or load. Oura's Readiness Score names 5 of the six inputs: HRV, resting heart rate, sleep, temperature and activity or load. "The sum of these daily Readiness Contributors make up your Readiness Score." No weights are published. WHOOP's Recovery names 3 of the six inputs: HRV, resting heart rate and temperature. WHOOP lists the measurements that "factored into the score" but not how they are combined. Garmin's Training Readiness names 3 of the six inputs: HRV, sleep and activity or load. The manual lists the six factors. It does not say how they are weighted. Garmin's Body Battery names 3 of the six inputs: HRV, sleep and activity or load. The manual names the four inputs and nothing more. Garmin's Stress level is HRV only: a rescaled HRV number, not a mix. HRV is the only named input. How it maps to 0–100 is not published. Polar's Nightly Recharge (ANS charge) names 3 of the six inputs: HRV, resting heart rate and breathing rate. Polar ranks the three inputs by influence but does not give the weights. Fitbit's Daily Readiness Score names 3 of the six inputs: HRV, resting heart rate and sleep. Google names the three inputs and does not publish the formula. Samsung's Energy Score names 4 of the six inputs: HRV, resting heart rate, sleep and activity or load. Samsung lists the metrics the score combines and nothing about their weights. Ultrahuman's Recovery Score names 4 of the six inputs: HRV, resting heart rate, sleep and temperature. "Each is graded on its own; then the five combine into the 0 to 100 score." No weights are published. Apple's Readiness names 3 of the six inputs: HRV, sleep and activity or load. Apple names four inputs and publishes no formula. It has not said which statistic Recovery HRV uses. Elite HRV's HRV Score is HRV only: a rescaled HRV number, not a mix. The score is a rescaled ln(RMSSD), set so that "everyone fits in a 0 to 100 range" using over 6 million readings. The exact mapping is not given. Welltory's HRV Score is HRV only: a rescaled HRV number, not a mix. Welltory names lnRMSSD as the input and publishes no formula or thresholds.
Six inputs cover what the makers name: HRV, resting heart rate Resting heart rate How many times your heart beats per minute while you are fully at rest. For adults it is usually 60 to 100 beats per minute, and lower in well-trained athletes. More about Resting heart rate , breathing rate Breathing rate How many breaths you take a minute. It moves HRV on its own: slower, deeper breathing makes the beat-to-beat swing larger, and below about 9 breaths a minute it shifts from the HF band into LF. More about Breathing rate , sleep, temperature, and activity or training load. A tick means the maker names that input for the score; a dash means it does not. Where a maker names something outside the six, such as blood oxygen, the panel says so.
What the scores have in common
HRV is in all of them. Oura’s Readiness uses HRV Balance, a two-week average against three months. WHOOP’s developer documentation lists heart rate variability among the measurements that factored into Recovery. Garmin’s Training Readiness takes HRV Status, and its Body Battery and stress level both start from heart rate variability. Polar’s ANS Autonomic nervous system The part of the nervous system that runs the body without conscious control, including heart rate. HRV mostly reflects how it adjusts the heart from moment to moment. More about Autonomic nervous system charge, Fitbit’s Daily Readiness, Samsung’s Energy Score, Ultrahuman’s Recovery Score Readiness score A single number, often out of 100, that a device builds from your HRV, resting heart rate, sleep and other inputs to suggest how ready you are for the day. The weighting is not published. More about Readiness score and Apple’s readiness all name it. Elite HRV’s and Welltory’s scores are HRV and nothing else, rescaled from lnRMSSD lnRMSSD The natural logarithm of RMSSD, with no unit. Taking the log evens out the spread of RMSSD values, which makes day-to-day changes easier to compare and analyse. More about lnRMSSD . What is an HRV score out of 100 covers those two.
Most add resting heart rate and sleep. Polar says heart rate has the biggest influence on its ANS charge and breathing rate the smallest. Oura counts four sleep-related contributors. Fitbit’s updated algorithm uses HRV, resting heart rate and sleep and dropped activity. Garmin’s Training Readiness counts last night’s sleep score and the last three nights.
Some add temperature or activity. Oura, Ultrahuman and WHOOP (on 4.0 and later) use skin temperature. Oura, Garmin, Samsung and Apple count recent activity or training load. Garmin’s Body Battery says food and caffeine have no effect.
None publishes the formula. Oura: “The sum of these daily Readiness Contributors make up your Readiness Score.” Garmin lists six factors. Polar ranks three inputs. Ultrahuman: “Each is graded on its own; then the five combine into the 0 to 100 score.” Nowhere is a weight given.
How HRV goes into a score: the baselines
A score does not use your HRV in milliseconds. It uses how tonight compares with your own past, and every maker remembers a different stretch of it.
| Maker | What it compares | Memory |
|---|---|---|
| Oura (HRV Balance) | Rolling average of the past two weeks, more weight on recent days | Past three months |
| Garmin (HRV Status) | Seven-day average | Baseline range from three weeks of sleep |
| Polar (ANS charge) | Each night | Your usual level over the past 28 days |
| Fitbit (Daily Readiness) | Each night | A baseline from seven nights, more accurate after a month |
| Ultrahuman (HRV Form) | Last night | Your HRV baseline |
| Apple (overnight vitals) | Recovery HRV | Your personal baseline |
A longer memory makes a score steadier and slower. Oura’s two-week window barely notices one bad night; Polar’s single-night comparison reacts to it at once. Both are reasonable designs, and they will disagree on the morning after a late evening. What is Oura HRV Balance and what an unbalanced HRV status means go through two of these in detail, and how long a baseline takes lists the waiting times.
The scales
| Score | Scale |
|---|---|
| Oura Readiness | 0 to 100: 85 and above optimal, 70 to 84 good, under 70 pay attention |
| WHOOP Recovery | 0 to 100% |
| Garmin Training Readiness | 1 to 100: prime, high, moderate, low, poor |
| Garmin Body Battery | 5 to 100: very low, low, medium, high reserve |
| Garmin stress level | 0 to 100: resting, low, medium, high |
| Polar ANS charge | −10 to +10, zero is your usual level |
| Fitbit Daily Readiness | 0 (low) to 100 (high) |
| Ultrahuman Recovery Score | 0 to 100 |
| Apple readiness | 0 to 10 |
| Elite HRV HRV Score | 0 to 100, rescaled lnRMSSD |
Because the scales and the inputs differ, a WHOOP Recovery of 60% and an Oura Readiness of 60 are not the same thing, and a Polar ANS charge of +3 cannot be placed on either.
Why two devices disagree on the same night
- Different HRV. Even the raw overnight RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next, in milliseconds. It mainly reflects vagal activity. More about RMSSD differs between devices. In Dial and colleagues’ 2025 study of 536 nights against an ECG ECG A recording of the heart's electrical activity, taken with electrodes on the skin. ECG-based RR intervals are the reference standard for measuring HRV. More about ECG , the average error was about 6% for Oura Gen 4, 8% for WHOOP 4.0, 11% for the Garmin Fenix 6 and 16% for the Polar Grit X Pro, and each device averages a different part of the night. HRV by device has the table.
- Different inputs. A short night with a high HRV scores well on a device that weights HRV and badly on one that weights sleep.
- Different memories. A two-week window and a one-night comparison react on different days.
- Different scales. The same state maps to different numbers.
What a score cannot tell you
A score is a summary of measurements, not a measurement. It cannot tell you whether a high HRV is good: Le Meur and colleagues found that 13 triathletes who did three weeks of overload training lost about 9% of their running performance while their weekly HRV rose, and a score built on HRV would have looked fine. It cannot tell you why a number moved; it can only show the contributors. And it has not been tested as a predictor of your performance or illness in any maker’s documentation. Which recovery score should I trust answers the question the title asks.
How to use a score well
- Open the contributors every time the score surprises you, and find the one that moved.
- Track the HRV in milliseconds and the resting heart rate as 7-day trends. Those are the measurements; the lesson on building your HRV baseline shows how.
- Keep one device for decisions. A second device teaches you about formulas, not about your body.
- Read any score next to how you feel and how training went. Should I train when my HRV is low gives a simple rule.
When to talk to a doctor
No score diagnoses illness or overtraining. Talk to a doctor if low scores come with feeling unwell, lasting fatigue, palpitations, dizziness or chest pain, whatever the number.