BAC Estimation shows an estimated Blood Alcohol Content during an active session, computed on your device from your logged drinks, body weight, and biological sex using the Widmark formula. This tutorial covers turning it on, setting up your profile, reading the live estimate, and setting an optional alert.
One thing first, because it matters more than anything else in this guide: this is an estimate for personal awareness only. It is not a measurement, not medical or legal advice, and it cannot tell you whether you are safe or legal to drive. Real blood alcohol depends on many things AlcoLog cannot know. Estimate only. Don’t drive.
# Step 1. Turn on BAC Estimation
If you are a new user, BAC Estimation is offered during onboarding. If you already have the app, open the Alerts tab and find the BAC Estimation section, then turn on Show BAC on Home.
The first time you enable it, AlcoLog shows a full-screen notice explaining what the estimate is and is not. You have to read and accept it before the feature turns on. This is deliberate: the estimate is only useful if you understand its limits.
Estimated BAC during a session
Notify me at a threshold I choose
# Step 2. Set up your profile
For the estimate to mean anything, AlcoLog needs two things: your body weight and your biological sex. These feed the Widmark formula. You can enter them by hand, or pull weight and biological sex from Apple Health if you have them stored there.
Your profile lives in BAC Estimation Settings, reachable from the BAC section in Alerts. You can change it any time, and you can turn the whole feature off from the same screen.
# Step 3. Read the live estimate
Once it is on and your profile is set, start a session and log a drink. An Estimated BAC card appears on your Home screen. It shows your current estimate, a colored bar, and whether the estimate is Rising or Declining. It updates as time passes and as you log more drinks, and it carries the Estimate only. Don’t drive. line at all times.
The number is a model, not a reading from your body. It will not match a breathalyzer, and it is never shown against a legal limit.
# Step 4. Set an optional alert
If you want a nudge, turn on BAC Alert in the BAC section and pick a threshold. The picker offers values in small steps, with the caption “Pick a number that matters to you. This is not legal advice.” When your estimate crosses the number you chose, AlcoLog sends a notification.
The default is deliberately conservative. The threshold is a personal marker you set for your own awareness. It is not a safe-to-drive line, because there is no such thing here. Estimate only. Don’t drive.
# Step 5. Privacy and the boundary
Your BAC estimate is computed on your device and stays there. There is no account, and the estimate is never shared, the same as the rest of AlcoLog.
To recap the boundary, because it is the whole point: BAC Estimation is a personal-awareness estimate. It cannot tell you whether you are okay to drive, it is never compared to a legal limit, and it is not medical or legal advice. If you have been drinking, do not drive.
# What’s next
To see BAC and your other session stats on your wrist, see using AlcoLog on Apple Watch. For the rest of the alerts system, see setting up alerts and notifications.