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Free intermittent fasting timer

Start a 16:8 fast in one tap and watch your eating window and fat-burning phases in real time. No download, no sign-up, works offline with local history.

  • No app
  • No account
  • Local history
  • Works offline
Timer not running00:00:00

Free, no account, no app. Your timer and history stay in this browser.

  1. Fed
  2. Early fasting
  3. Fat burning
  4. Ketosis
  5. Deep ketosis
Your on-device data

Back up, restore, or erase the timer data stored in this browser. Nothing is sent to a server.

Planning estimates only — see methodology for phase sources. Not medical advice.

How the fasting timer works

Pick a protocol (16:8 is the most popular), tap start, and the timer tracks your fast in real time. As the hours pass, your body typically moves through several metabolic phases. These are general estimates and vary from person to person.

  1. Pick a protocol

    Choose a fasting window that fits your day. 16:8 is the most common starting point, and you can switch any time.

  2. Start with one tap

    The timer runs right in this browser — no download, no account. Your session and history stay on this device.

  3. Follow the phases

    Watch estimated metabolic phases unfold as the hours pass, then end or adjust your fast whenever you choose.

Metabolic phases during a fast

  • Fed

    from about 0h

  • Early fasting

    from about 4h

  • Fat burning

    from about 12h

  • Ketosis

    from about 16h

  • Deep ketosis

    from about 24h

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