Fitbit Flex™ features five LED indicators. These lights give you information about what the tracker is doing.
Checking goal progress
When you tap Flex to check your progress towards your daily activity goal, each solid light represents a 20% increment toward that goal. For example, if your goal is 10,000 steps, three solid lights means you're approximately 60% of the way there and you've taken about 6,000 steps. When you feel Flex vibrate and it starts flashing, you'll know you've reached your daily goal.
Using manual sleep mode
Flex tracks sleep automatically without any action on your part. If you want to know how long it takes you to fall asleep, put Flex into sleep mode manually. To do so, tap it rapidly for one or two seconds until it vibrates and shows two slowly dimming lights. Throughout the night, two blinking lights will alternate. To exit manual sleep mode in the morning, rapidly tap Flex. It will vibrate, flash all five lights three times, and then display a spinning light pattern.
These light patterns apply to manual sleep mode only. If you let Flex automatically detect your sleep, you won't see any special light patterns during the night.
Charging the battery
While Flex is charging, a light will pulse to show the battery level every few seconds. Each light represents progress towards the total charge. When the battery is fully charged, all 5 lights will blink.
Confirming a silent alarm
When a silent alarm goes off, Flex vibrates and the center light flashes.