Frequently Asked Questions

To ensure optimal performance and longevity of your Calibre device, always use the provided USB-C charging cable and a standard 5V-2Amp max (non-accelerated) charging block, plugging it directly into a wall socket. Avoid using third-party cables or charging through laptops and external devices, as these may not charge the device correctly and could lead to damage or battery degradation. Charge your Calibre device for 2-3 hours, and check for a solid white light to confirm a full charge.

Calibre has multiple sensors inside. One of them measures the flow of your breath, 50 times per second, to ensure accurate real-time readings. Other sensors independently measure oxygen concentration, CO2 concentration, barometric pressure, humidity and temperature. All of these are important for obtaining an accurate analysis of the metabolic content of your breath.

Calibre has already been validated in an independent study by a team from the University of Maastricht (Netherlands) in 2023. The third-party, peer-reviewed results were published in the Scandanavian Journal of Medicine & Science in Sport.  In addition to that study, we’re actively working to arrange further third-party validation with three additional universities. Our goal is to complete this testing during 2025. However, recent funding cuts to U.S.-based research programs have introduced some logistical challenges, which may impact the timeline. We’ll share updates as soon as we have more clarity on the process.

Calibre has been designed for individual use. You can clean and disinfect the facepiece and straps. We have not conducted any studies to test the infection risk of the module, therefore we cannot claim Calibre to be suitable and safe for users to share one device with multiple people. If you choose to do so, it is at your own risk.

Calibre is the first device that democratizes access to respiratory and metabolic data. By utilizing a radical new design for managing air flow, incorporating top of the line medical grade sensors, and corresponding computational methods, Calibre has created a portable, light-weight, and cost-effective way to capture this data individually or at scale.

We’re excited to share that we’ve recently added heart rate monitor integration to enhance data tracking. Currently, we support the Polar Verity Sense, Polar H10, and Myzone Switch HRMs, with additional integration options on the way.

Calibre is engineered for optimal performance in indoor or controlled environments. Outdoor settings introduce factors that are more challenging to control, which could potentially interfere with some of the measurements.

Strong direct airflow from fans, outdoor wind, or fast motion (e.g., cycling) can distort the device’s measurements. To ensure accurate readings, avoid exposure to such sources of wind during your sessions. Air conditioning does not impact the device’s performance. We are developing solutions to address these issues and will provide updates as improvements become available."

We recommend using your Calibre device in environments between 50°F (10°C) and 122°F (50°C) to ensure optimal performance. Temperatures outside this range may affect sensor accuracy and data reliability. Additionally, avoid using Calibre near pools or water sources to prevent moisture-related issues.

To maintain a stable Bluetooth connection, your Calibre device should stay within 10 feet (3 meters) of your phone. Moving beyond this range may result in data loss. We are actively working on extending this range and enabling continuous data recording even when the device is temporarily out of range. Stay tuned for future updates!

Yes, you can definitely use Calibre if you're a nose breather. It works equally well whether you're a mouth, nose, or mixed mouth and nose breather. The nose area depression on the facepiece is designed with a large enough opening so that air can easily flow through your nostrils into the facepiece. Just be sure you're not sticking your entire nose inside the opening like a scuba or snorkeling mask, let the facepiece rest gently under the nose.

Calibre is designed to minimize any restriction of air flow for maximum breathing comfort and usability during exercise and normal day to day activities. Most users agree there is virtually no detectable restriction of breath. In the mask design itself you can see the pass-through holes that were created to facilitate this capability.

At the moment, we only offer one size ("medium") for the facepiece, and we recognize that it will not fit everyone equally well. We plan to introduce additional sizes in the future, but those are not yet available.

The combined weight of the facepiece & module is under 2 ounces and it is slightly over 4" wide.

No, Calibre does not require any O₂ or CO₂ sensor replacements, and there are no consumables that need regular replacement. The device is designed to operate without regular servicing. However, it comes with a 1-year warranty, and if any reasonable repair or replacement is needed within that time frame, we’re happy to assist.

You can delete your Calibre account in one of two ways:
Option 1 – From the Calibre app:
1. Open the app and go to your profile page.
2. Tap “Manage Account” at the bottom — this will redirect you to the web portal login page.
3. Log in with your Calibre credentials.
4. Go to the Security tab, scroll down, and select “Delete” under the Delete Account section.

Option 2 – From the web portal:
1. Visit the Calibre web portal and log in with your Calibre credentials.
2. Click your account icon in the top right and go to Account.
3. Go to the Security tab, scroll down, and select “Delete” under the Delete Account section.

Please note: Deleting your account will permanently erase all associated data and cannot be undone."

Please refer to the user manual and the Getting Started page for all set-up information.

To ensure full compatibility and reliable performance, your device must meet the following requirements:

Operating System
• Android: Version 12 or higher
• iOS: Version 15.4 or higher

Devices that do not meet these requirements may be unable to install the app or may experience pairing and performance issues.

Calibre connects to the app via Bluetooth (BLE). It does not require internet or cellular network coverage to function.

While the Calibre app may function on iPads and Android tablets, it was specifically designed for use on smartphones. Because of this, we can’t guarantee full compatibility or performance on tablet devices. For the best experience, we recommend using the app on a supported iPhone or Android smartphone.

Yes, to ensure accurate measurements, calibrate your Calibre device before each use, in the same environment where you will be testing. Avoid breathing into the device for at least 30 minutes prior to calibration. Place the device on a stable surface, away from any wind, fans, or exhaled breath during the calibration process.

The calibration process is simple and relies on ambient room air—no separate calibration gas is needed. The app will prompt you to calibrate before starting a recording. During calibration, you'll see a side-to-side yellow light on the device.

To ensure the highest accuracy for O2 and CO2 metrics, the sensors need a few minutes to stabilize before you start recording. During this time, you'll see loading spinners, and a warning will appear if you attempt to start too early. Waiting for the stabilization process to complete guarantees the best quality data for your session. If the sensors don’t stabilize within a few minutes, we recommend performing a Baseline and starting a new session. Just be sure to re-calibrate the device before starting again.

To perform a Baseline, follow these steps:
1. Press and hold the front button on your device for 10 seconds until you see a triple flash of yellow light on your device.
2. Let the device rest for 1 minute.
3. Charge the device for at least 30 minutes—this step is essential. The O2 sensor requires a full 30 minutes on the charger to warm up properly, even if the battery is already charged. Skipping this may lead to inaccurate readings.

To ensure proper operation and comfort, position the facepiece so it covers your mouth and rests gently just beneath your nostrils (without inserting your entire nose into the opening underneath).

It’s very important to understand that Calibre is designed to sit softly against the face. Unlike most breath-measuring devices that rely on a tight seal, Calibre should be held in place by the straps—gently, but snugly enough that it doesn’t fall away from your face. Avoid pressing or compressing the facepiece too much, as it needs a sufficient interior volume to measure accurately.

We regularly release firmware updates to improve performance, fix bugs, and enhance reliability. These updates are completed through a separate app called the Calibre Firmware Updater.

Quick Instructions
After connecting your device in the main Calibre app, you'll see your device details at the bottom of the screen. If a new firmware version is available, an Update button will appear. Tap it to launch the Firmware Updater app and follow the prompts to complete the update.

For complete instructions, view our step-by-step guide.

Step-by-Step Instructions
1. Download the Calibre Firmware Updater app
• Available on the App Store and Google Play Store

2. Connect your device in the main Calibre app
• Tap Start Measuring and follow the normal setup steps
• After your device connects, scroll to the bottom of the Calibrate screen
• If an update is available, an orange Update button will appear — tap it

3. Initiate the update
• Tap Start Update, then Open Calibre Updater
• This will launch the Firmware Updater app and put your device in update mode (you’ll see a side-to-side white light)Note: The device stays in update mode for only 1 minute. If the process doesn’t begin in that time, return to the Calibre app, reconnect the device, and try again

4. Complete the update * In the Firmware Updater app, select your device (labeled BLE DFU Device) and tap Pair
• Choose the available firmware version and tap Update
• Keep the app open and your device nearby during the process (usually takes 2–5 minutes)
• Once finished, you can return to the Calibre app to begin measuring again
Note: It may take up to 1 minute for your Calibre device to fully exit update mode before it’s ready to reconnect."

The device's battery life varies based on usage but typically lasts up to 36 hours on a full charge. To optimize the battery life and help ensure your device is adequately charged for your next session, here are a couple of tips depending on how often you use it:

Sleep Mode (More than once a day)
• Use this mode when the device will be inactive for short periods (e.g., between sessions or throughout the day).
• In between uses, place the device in sleep mode by holding the button for about 3 seconds until the light fades out. This keeps it in low-power mode while ensuring the sensor stays ready.

Shut-Down (Once a day or less)
• Ideal for overnight or long-term storage (e.g., more than a day without use).
• Fully power off the device by holding the button for approximately 10 seconds until you see a triple-flash yellow light.
• Important! Before your next session, be sure to charge the device for at least 30 minutes to properly warm up the O2 sensor. Skipping this step will lead to inaccurate data.

Red: The red LED light usually indicates low battery. You should fully charge your device.

Side-to-Side Yellow: Calibre is undergoing calibration. For proper calibration it should be placed on a stable surface and left undisturbed until calibration is complete and yellow light stops flashing.

Flashing Yellow: The device is fully powered off. Must allow a 30 minute charge before next session to properly warm up the O2 sensor.

Flashing White: The flashing white LED light means your Calibre is ready to connect to the phone app and has not yet made the connection.

Oscillating White: The slowly oscillating white LED light indicates your Calibre is charging.Solid White: The solid white LED light indicates your Calibre is fully charged."

Do not wash, rinse, or submerge the module, as this could damage the internal electronic components and void the warranty. However, the facepiece and other non-electronic parts are waterproof and washable.

You may clean the facepiece as often as needed, as long as the module is removed. Soap and detergent are safe to use—just be sure to rinse thoroughly and let it dry completely before reattaching the module.

The washable parts can also be placed in a dishwasher or laundry machine, but we do not recommend drying them at excessively high temperatures, as this may damage the material."

To prevent water damage and ensure proper functioning, always insert one of the provided silicone plugs into the USB-C port before using your Calibre device. This plug acts as a barrier to safeguard the internal electronics from moisture. Wipe any excess moisture from the outside of the module before charging, and ensure the module is dry before connecting it to a power source.

It's normal for the button not to indent completely, as it's designed to respond with a light touch rather than a full click. I know this can take some getting used to but rest assured that it's functioning as intended.

Calibre continuously measures air flow, breath rate (50 times per second), oxygen and CO2 levels, temperature, and pressure, essential for accurate metabolic analysis. All these quantities allow us to calculate an extensive list of metrics, such as real-time values of calorie burn, VO2, VCO2, minute volume, and more. When these measurements are performed over a period of time we can further calculate useful cumulative, average, and max/min values, such as average breath rate, peak and average VO2 achieved. For a complete list of the metrics Calibre measures and calculates, refer to this PDF.

To get accurate, lab-grade data from Calibre, it's important to follow a few key steps — especially during setup. Calibre is a precision metabolic measurement device, and unlike causal fitness wearables, it requires proper preparation to function as intended.

We’ve created a Setup Checklist to walk you through everything you need to do before each session. Skipping steps can lead to inaccurate results, while following the full process ensures you're getting the high-quality data Calibre is designed to provide.

You can also visit our Getting Started page for additional best practice and setup guidance.

The calories you burn result from oxygen combining with nutrient fuels in your body - sugar and fats - while producing CO2. By measuring both the oxygen absorbed and the CO2 released by your body, we can determine in real time how much energy is utilized. This scientific technique called "breath calorimetry" has been validated and used by experts for decades.

In earlier versions of the Calibre app, Fat Burn % and Carb Burn % always added up to 100%, using a common formula based on your Respiratory Exchange Ratio (RER = VCO₂ / VO₂):
• Carb Burn % = 0% when RER < 0.7 and 100% when RER > 1.0
• Fat Burn % = 100 – Carb Burn %

While this model is widely used, it’s a simplification. In reality, protein also contributes to energy metabolism. Protein metabolism isn’t directly measurable from breath, but it can be estimated based on factors like body weight and an average diet. In developing the new Calibre app, we consulted with experts in the field. Together, we concluded that including estimated protein contribution provides a more accurate representation of your energy usage.

As a result, Fat Burn % + Carb Burn % now typically adds up to less than 100%—the difference reflects estimated protein metabolism.

Note: Protein metabolism can be measured more precisely through laboratory testing, but not in real time during breath analysis.

Tidal volume refers to the amount of air you inhale or exhale in a single breath. When measuring exhaled gases like carbon dioxide (CO2), there are different ways to analyze the breath. One common measure is end-tidal CO2 (EtCO2) — sometimes referred to as end-tidal volume measurement — which reflects the concentration of CO2 at the very end of an exhalation — this is typically where CO2 levels peak.

Most quantities of interest in metabolic measurements, however, are based on FeCO2, which represents the total or average CO2 concentration across the entire exhaled breath. Calibre is designed to calculate accurate average CO2 levels (FeCO2) by analyzing and averaging exhaled air over time, rather than isolating the brief window at the end of each breath needed for EtCO2 measurement.

This design choice helps improve overall accuracy for metabolic assessments, though it means Calibre does not provide specific EtCO2 values in its current form.

For maximum accuracy, we strongly recommend performing a Baseling before each use. This ensures the sensors are properly warmed, resulting in the most precise measurements.

How to Perform a Baseline:
1. Press and hold the front button for 10 seconds until you see a triple-flash yellow light.
2. Let the device rest for 1 minute.
3. Charge the device for at least 30 minutes—this step is essential. The O₂ sensor requires a full 30 minutes on the charger to warm up properly, even if the battery is already charged. Skipping this may lead to inaccurate readings.

Yes, utilizing our validated protocol allows you to measure and calcualte your VO2Max accurately.

Due to data averaging requirements, the device needs a minimum session time of 5 minutes to provide the most accurate results. To achieve the best and most reliable overview of all metrics, ensure you meet this duration.

While longer session durations are generally well within the capabilities of Calibre, we've seen numerous cases – primarily associated with high-intensity exercise – where sensor readings become increasingly saturated after about 25 minutes. This is due to excessive water buildup (from breath condensation and perspiration) entering the sensing module.

Continued use under these conditions is not recommended. We are working to extend these limitations, but in the meantime, to ensure accurate readings and maintain device performance, follow these guidelines:
• Moderate intensity (≤ 60 L/min breath volume, up to 10 METs): Up to 90 minutes without issues.
• High intensity (> 60 L/min breath volume): Maximum 25 minutes, including warm-up, cool-down, and all activity.

Back-to-back sessions should be treated the same as a single extended session. To prevent sensor interference from moisture buildup, we recommend waiting at least 1 hour between sessions.

METs, or Metabolic Equivalents, are a measure of the energy cost of physical activities, such as cycling, running, or other exercises. Many mainstream training devices, like treadmills, stationary bikes, and rowing machines, display this metric.

One MET is defined as the energy expenditure at rest, typically around 3.5 mL of oxygen consumed per kilogram of body weight per minute. In cycling, METs are used to quantify the intensity of the activity.Understanding and utilizing METs will vary depending on your fitness level.

For example, in cycling a relatively fit person could see the following:
• Light cycling (e.g., leisurely ride): Around 3-6 METs.
• Moderate cycling (e.g., a steady pace): Around 6-8 METs.
• Vigorous cycling (e.g., racing or intense effort): 8+ METs.

Professional cyclists often reach very high MET levels due to the intensity and duration of their training and competition. MET levels for pro cyclists can vary significantly depending on the activity and effort level:
1. Low-Intensity Training or Recovery Rides:
• METs: 6-8
• Examples: Easy rides or warm-up/cool-down sessions where the intensity is kept low.

2. Moderate-Intensity Training:
• METs: 8-12
• Examples: Steady-state rides or endurance training at a moderate pace.
3. High-Intensity Training:
• METs: 12-16
• Examples: Tempo rides, time trials, or sustained climbing efforts.
4. Maximal Effort (e.g., Sprints, Hill Climbs):
• METs: 16+
• Examples: All-out efforts during a race, sprint finishes, or intense hill climbs.

In peak performance scenarios, such as during a grueling stage of a grand tour, pro cyclists can sustain MET levels above 16 for extended periods, reflecting their exceptional aerobic capacity and conditioning.

Training with METs helps cyclists (athletes) gauge and adjust the intensity of their workouts, monitor energy expenditure, and tailor training programs to meet specific fitness goals.

Yes, you may export your session data as CSV files through your personal web-based portal:
1. Go to the web-based portal
2. Log in with your Calibre app credentials.
3. Select the download button next to the session or open the session and select “Download CSV”."

If your device is unresponsive, follow these charging guidelines first:Use the provided USB-C cable (avoid third-party cables).

Use a standard 5V-2A charging adapter (avoid accelerated adapters).Plug directly into a wall socket (avoid external charging devices).

Charge for at least 2-3 hours, regardless of LED light status.

If the device remains unresponsive, perform an overnight charge (minimum 8 hours) and follow these steps:
• Charge the device overnight or for a minimum of 8 hours using the provided cable and a standard 5V-2A charging block plugged directly into a wall socket.
• The next morning, unplug the device from the charger.
• Press and hold the front button on your device for 10 seconds until you see a triple flash of yellow light on your device. If no flash occurs, continue to the next step.
• Let your device rest for 10 minutes.
• Charge the device for at least 30 minutes, even if it is already fully charged. This step is crucial, as the O2 sensor needs at least 30 minutes on the charger to warm up properly, regardless of the battery status.

If your device still does not respond or display a white light when pressing the button, please contact us at info@calibrebio.com for further assistance.

If your device displays a solid or blinking red light, follow these charging guidelines first:
• Use the provided USB-C cable (avoid third-party cables).
• Use a standard 5V-2A charging adapter (avoid accelerated adapters).
• Plug directly into a wall socket (avoid external charging devices).
• Charge for at least 2-3 hours, regardless of LED light status.

If the red light persists, perform an overnight charge (minimum 8 hours) and follow these steps:
• Charge the device overnight or for a minimum of 8 hours using the provided cable and a standard 5V-2A charging block plugged directly into a wall socket.
• The next morning, unplug the device from the charger.
• Press and hold the front button on your device for 10 seconds until you see a triple flash of yellow light on your device. If no flash occurs, continue to the next step.
• Let your device rest for 10 minutes.Charge the device for at least 30 minutes, even if it is already fully charged. This step is crucial, as the O2 sensor needs at least 30 minutes on the charger to warm up properly, regardless of the battery status.

If the issue persists, please contact us at info@calibrebio.com for further assistance.

The device's battery life varies based on usage but typically lasts up to 36 hours on a full charge.

If you believe your battery is depleting faster than normal, the first thing to do is ensure you are following these charging practices:
• Use the provided USB-C cable (avoid third-party cables).
• Use a standard 5V-2A charging adapter (avoid accelerated adapters).
• Plug directly into a wall socket (avoid external charging devices).
• Charge for at least 2-3 hours, regardless of LED light status.Put the device in sleep mode when not in use (press and hold the button for 3 seconds until the light fades).

If you’re following all of the above charging practices and your battery still depletes faster than intended, please conduct an battery test:
• Charge the device overnight or for a minimum of 8 hours using the provided cable and a standard 5V-2A charging block plugged directly into a wall socket.
• Disconnect the device from the charger and promptly place it in sleep mode. (To activate sleep mode, press and hold the device's button for approximately 3 seconds until the light illuminates, then release the button once the light fades).
• After 24 hours, connect your device to the app, note the battery percentage, and report it to the Calibre team at info@calibrebio.com.

The shipping rate will vary based on your zip code and country. Calibre does not cover VAT, customs, or import taxes. When you make your purchase, we are unable to calculate your local VAT, customs, or import taxes, so please ensure that you perform your own due diligence in paying these charges upon receiving your package.

If you received a product that is damaged or faulty, you may exchange it for a new one within 30 days.