Fitbit Aria 2 is the Wireless Smart Scale that uses advanced technology to measure weight, body fat percentage, and body mass index (BMI) to help you take control of your fitness.
Aria 2 has two modes to calculate body fat. The default is “regular” mode, which applies to most people. This mode works well for people who don't get a great deal of exercise as well as those who exercise frequently.
“Lean” mode is intended for professional or very high-level athletes like marathon runners or body builders. Individuals with exceptionally low body fat relative to their muscle mass may want to consider lean mode; however, many very fit and active people get accurate readings in regular mode.
If the mode you selected appears to be giving you an incorrect body fat percentage reading, try switching modes. For instructions on how to switch your scale's mode, choose a section below.
- Tap the Today tab
, and tap devices
.
- Tap Aria 2.
- Tap People Using This Scale.
- Tap your name.
- Turn Lean Mode on or off. The next time you weigh in and the scale syncs, the mode switches and your body fat percentage is calculated with the mode you selected.
, and tap devices 
.- On the Fitbit settings page, click Aria 2.
- Click the People tab.
- Click your name.
- Select the appropriate mode. The next time you weigh in and the scale syncs, the mode switches and your body fat percentage is calculated with the mode you selected.
Each time you weigh yourself with Aria 2, the scale shows your weight. You can choose to have the scale display your body fat percentage and BMI as well.
Body fat percentage is the mass of your fat divided by your total body mass. It's estimated using bioelectrical impedance analysis, which sends a small, safe signal through your body. Generally, a body fat percentage between 10-22% for men and 20-32% for women is considered healthy (source).
BMI is calculated using weight and height to provide a number that categorizes individuals as underweight, normal weight, overweight, or obese. A BMI between 18.5 and 24.9 is considered normal (source).
To adjust whether body fat percentage and BMI are shown on the scale:
- Tap the Today tab
- Tap Aria 2.
- Tap People Using This Scale.
- Tap your name.
- Choose to show body fat percentage and BMI on your scale. The next time you weigh in and the scale syncs, the settings are saved.
Aria 2 can sync with up to 8 different Fitbit accounts. By syncing with your Fitbit account, you can track your weight, body fat percentage, and BMI over time. Other individuals may use the scale to weigh themselves (body fat percentage and BMI won't appear), but their measurements aren't saved or synced with a Fitbit account.
To invite others to use your scale, see How do I use my Fitbit scale?
For security purposes, if you give away or recycle your Aria 2, make sure you first remove any personal data. To erase your scale:
- Turn your scale over and pull up on the tab to remove the cover from the battery compartment.
- Remove the batteries.
- Press down on the small button directly above the battery slots.
- While continuing to press down on the button, reinsert the batteries. Be sure to press the button for at least 10 seconds.
- Return the cover to the battery compartment and press down until it’s secure.
- Turn your scale over. You should be prompted to begin the setup process.
Aria 2 should always be stored flat. When the scale is stored vertically, it must recalibrate before you see accurate measurements. If you move the scale or store it vertically, you may need to perform 2 consecutive weigh-ins to recalibrate the scale.
Clean Aria 2 as needed to remove dust and soil. To clean your scale, follow these tips:
- Wipe down the surface with a damp cloth using a mild detergent before your first use.
- Do not submerge Aria 2 or use high-pressure water jets (e.g. shower head) to clean the surface.
- Do not use antiseptic wipes, chlorine, or highly concentrated glass cleaner on the surface of the scale.
- Do not use abrasive cleaners to clean your scale.