Nightcap live BAC tracker
Sober No drinks yet
Right now
0.000 % BAC
Sober
    Once fully absorbed
    0.000 % BAC
    —

      Log your first drink below to start the night.

      0.000.040.080.150.30+
      Peak so far 0.000
      Time to 0.05 —
      Sober in —
      Drinks · Calories 0 · 0 kcal

      Add a drink

      Tap a category to start

      Timeline

      Your drinks, water, and food will appear here in order.

      Important

      This is an estimate based on the Widmark formula and an average elimination rate of 0.015% BAC per hour. Real BAC varies with food, hydration, medication, genetics, and many other factors. If you've been drinking, don't drive. Use a rideshare, taxi, or designated driver. When in doubt, wait longer.

      Your profile

      Affects body-water distribution (Widmark r-factor).

      Logging "Food" in the timeline switches you to "Light meal" automatically.

      Friends supporting friends. Everyone keeps their own log on this device, side-by-side, so you can spot when someone needs to slow down.

      Drinkers Add friends so you can pace each other through the night.

      Get notified when your BAC crosses 0.05, 0.08, or 0.10 — and again when it falls back below 0.05 or to zero.

      In-app alerts Shows a banner inside Nightcap.
      System notifications Required to alert when the tab is hidden.

      Cover image

      Pick the mood for your splash screen and recap card.

      Your data

      Export session history Download a CSV of every saved night for your records.

      Your profile, sessions, and badges live entirely on this device. Nothing is uploaded.

      About & legal

      Terms of use & limitation of liability

      Nightcap is an estimate. It is not a breathalyzer, a medical device, or legal advice.

      The blood-alcohol concentration shown is computed from the Widmark formula using the body and drink data you enter. Real-world BAC depends on dozens of factors Nightcap cannot see — medication, hydration, sleep, illness, hormones, body composition, what you actually drank, and how the bartender poured it.

      Never drive based on this app. If you have been drinking, use a rideshare, taxi, public transit, or a sober friend. When in doubt, wait longer than the app suggests.

      Nightcap and its makers are not liable for any harm, injury, arrest, fine, accident, illness, or other consequence arising from your use of — or reliance on — the information shown here. By continuing to use Nightcap you agree to use it as a harm-reduction tool only and to take full responsibility for your own decisions.

      Nightcap does not collect, transmit, or sell any personal data. Your profile lives only in this browser tab's URL hash; your session history and badges live in this browser's local IndexedDB. Clearing your browser data clears Nightcap.

      If you do not agree, please close the app.

      Privacy

      Nightcap runs entirely in your browser. There is no account, no server, no analytics, and no third-party tracker. The app cannot tell anyone (including us) that you used it.

      Where your data lives:

      • Profile (name, body type, weight, region, legal limit, cover preference): URL hash on this tab.
      • Tonight's session and saved past sessions: this browser's IndexedDB.
      • Earned badges: this browser's IndexedDB.

      Nothing leaves the device. To wipe everything, clear site data for this URL.

      Nightcap · v1.1 · harm-reduction information only.

      Tonight

      Adjust your stomach state or drive-home time without leaving the night.

      Onboarding

      Wipe your saved profile and replay the splash + setup screens.

      Shift the whole session

      Moves the first drink to the chosen time. Every other event shifts by the same amount so the spacing between drinks is preserved. To change a single drink, tap its time in the timeline.

      or

      If the time is later than now, we'll assume yesterday.

      Edit time

      Mark when this was actually consumed. BAC will recalculate.

      or

      If the time is later than now, we'll assume yesterday.

      Pick a drink

      Styles
      Brands

      Custom drink

      Wrap up the night

      Saving keeps tonight in your history. We don’t share it.

      Plan tonight

      Please don’t drink and drive. This is a hypothetical, non-scientifically tested warning system — not a license for dangerous activity. Call a car.

      Tonight’s setup

      Two quick questions for a more accurate read.

      1
      Have you eaten?
      Food slows absorption — a full meal can lower your peak BAC by ~30%.
      2
      Are you driving?
      If yes, make a plan first — we’ll show you a safe ceiling.
      Please don’t drink and drive. This is a hypothetical, non-scientifically tested warning system — not a license for dangerous activity. Call a car.

      Add drinker

      Each drinker keeps their own BAC, drinks, and profile. Useful for tracking a friend or roommate alongside you.

      Drinkers

      Tap a name to switch the active drinker. Removing a drinker also clears their drinks for tonight.

        History