Lodestar

Guides

Plain-language guides to the numbers your Fitbit records: what they mean, why they move, and how to read them against your own normal.

Sleep

• How accurate is Fitbit sleep tracking?
  How well Fitbit sleep tracking matches lab sleep studies: good at total sleep, rougher on stages and awake time. How to read your sleep data with that in mind.
• How much REM sleep do you need?
  How much REM sleep most adults get, why it piles up near morning, what cuts it short, and how to read the REM number in your Fitbit sleep stages.
• How much deep sleep do you need?
  How much deep sleep adults usually get, why it falls with age, what your Fitbit deep sleep number can and can't tell you, and what actually helps.
• Sleep debt: how it adds up and how to pay it back
  What sleep debt is, how a few short nights add up, why one long lie-in doesn't clear it, and how to use your Fitbit sleep data to track and recover it.
• Why is my sleep score low when I slept all night?
  Slept a full night but your Fitbit sleep score is low? Why hours aren't the whole story: deep and REM sleep, time awake and heart rate in sleep.

Heart and HRV

• What your Fitbit HRV number means
  Your Fitbit HRV explained in plain language: what it measures, what's normal, why it moves, and how to read it against your own baseline.

Recovery and training

• A recovery score for your Fitbit, on iPhone
  How a daily recovery score works with Fitbit data: the signals that go into it, why your own baseline matters, and how to get one on iPhone.

Your Fitbit data

• How accurate are Fitbit calories burned?
  How your Fitbit estimates calories burned, why the number can be off by a lot, the difference between total and active calories, and how to use it sensibly.
• How to see your Fitbit data in more detail on iPhone
  Where your Fitbit data lives now, why the Fitbit app shows summaries, how other iPhone apps can read it with your permission, and what to ask first.
• Your Fitbit app stopped syncing? Here's why
  Google is switching off the old Fitbit Web API in 2026. What changed, why some third-party apps stopped syncing, and what you can do about it.

Lodestar is for general wellness and information only. It is not a medical device and does not diagnose, treat, cure or prevent any condition. Talk to a qualified health professional about any medical concern.