SipLogger is a free educational BAC calculator app and alcohol tracker for iPhone and iPad. Log a drink from 300+ templates and the estimated curve shows absorption, the peak, and the slow return to baseline, personalised by your weight, height, sex, and age with the Watson and Widmark formulas. Nothing leaves your device.
For educational and informational purposes only. Estimated values vary by about ±20% from measured ones and are never a basis for deciding whether to drive.
Each drink is timestamped and modelled on its own, the evening builds an estimated curve, and every session is kept for you to look back on.
Pick from 300+ drinks in six categories, or set any volume and ABV. Half, can, and pint portions are one tap, and the pace setting spreads a slow drink over the time it actually took.
The estimated curve updates as you log: the rise, the peak, and the long tail back to baseline, with the projected time it takes. Live Activities keep the session on the Lock Screen and in the Dynamic Island, and the finished evening is saved with its peak and duration.
Every session is kept with its drinks, grams of alcohol, estimated peak, and duration. Review months at a time and export the lot as CSV or JSON. It is your diary, and it stays on your device.
Everything is included from the first launch. There is no premium tier.
$0no subscription, no ads, no in-app purchases
SipLogger is free and complete. There is no account to create and no server behind the app, so there is nothing to pay for and nothing to cancel.
±20%typical variance of formula-based estimates
SipLogger measures nothing. It estimates from what you log and your profile, and formula estimates commonly differ from a measured value by about a fifth in either direction. Food, hydration, medication, and genetics all move the real number.
The four iPhone screens as they appear on the App Store: an active session, a past session, adding a drink, and the history.
SipLogger does not measure blood alcohol. It estimates it from the drinks you log and your body profile using the Watson total body water method and the Widmark formula, models used in clinical and forensic work for decades. Formula estimates typically vary by about 20 percent from a measured value, because food, hydration, medication, liver health, and genetics all change how alcohol is absorbed and cleared. Use SipLogger to understand how alcohol moves through a body over an evening, never to decide whether to drive or operate machinery. The accuracy guide explains where the variance comes from and how to read the curve.
Yes, SipLogger is 100% free with no subscription fees, no ads, and no in-app purchases. It is an educational tool for understanding alcohol metabolism. All features are available immediately with no restrictions.
SipLogger uses the Watson Total Body Water (TBW) method combined with the Widmark formula to estimate blood alcohol content. The calculation considers your weight, height, biological sex, and age to model how alcohol is absorbed and metabolized over time. Results are educational estimates with approximately ±20% accuracy.
The estimated BAC has approximately ±20% accuracy. Individual metabolism varies based on many factors including food intake, hydration, medications, liver health, and genetics. SipLogger is for educational and informational purposes only — never use estimated BAC to make decisions about driving or operating machinery. Read our full guide to BAC calculator accuracy.
No. SipLogger is an educational tool and never provides driving advice. The app shows when your estimated BAC approaches baseline levels, but this should never be used to determine fitness to drive. Always use a certified breathalyzer or wait a safe amount of time. When in doubt, use a taxi or rideshare.
Yes, SipLogger has no backend servers, requires no account, and collects no data. All your drink logs and session history stay entirely on your device. HealthKit data is read-only and never leaves your device. The app contains no analytics, no tracking, and no third-party SDKs.
SipLogger optionally reads weight, height, biological sex, and date of birth from HealthKit to improve estimated BAC accuracy. This data is only used locally for calculations — it is never transmitted, stored externally, or shared. SipLogger never writes data to HealthKit.
SipLogger includes 300+ built-in drink templates covering beer, wine, spirits, cocktails, and more. Each template has pre-configured volume and alcohol percentage. You can also create custom drinks with any volume and ABV percentage.
The Widmark formula is a well-established pharmacokinetic model for estimating blood alcohol content. It calculates estimated BAC based on the amount of alcohol consumed, body weight, a gender-specific distribution ratio, and time elapsed. SipLogger enhances this with the Watson Total Body Water method for improved body water estimation, making it a reliable educational tool. Learn more in The Widmark Formula Explained.
Yes, SipLogger is a universal app that works on both iPhone and iPad. The interface adapts to larger screens for a comfortable experience on iPad.
SipLogger is rated 18+ on the App Store. The app is intended for adults of legal drinking age. It is an educational and informational tool — it does not encourage or promote alcohol consumption.
SipLogger is a free educational BAC calculator for iPhone that uses the Watson TBW and Widmark formula to estimate blood alcohol content over time. Unlike many alternatives, SipLogger has no ads, no subscription, no in-app purchases, and collects no data. It includes 300+ drink templates, a real-time BAC curve, Live Activities, HealthKit integration, and is available in 11 languages.
SipLogger shows your estimated BAC curve over time so you can see when your level is projected to approach baseline. Alcohol is generally metabolized at roughly 0.015% BAC per hour, but individual rates vary. SipLogger models this using the Watson TBW and Widmark formula personalized to your body. This is an educational estimate only — never rely on any app or calculator to determine fitness to drive.
No. SipLogger is not a breathalyzer and does not measure actual blood alcohol. It is an educational calculator that mathematically estimates BAC based on your drinks, body parameters, and time using the Watson TBW and Widmark formula. Results have approximately ±20% variance. For precise measurement, use a certified breathalyzer device.
Yes. SipLogger uses Live Activities to show your current estimated BAC and session timer on your iPhone Lock Screen and Dynamic Island. This lets you monitor your estimated level at a glance without opening the app.
A standard drink contains approximately 14 grams (0.6 oz) of pure alcohol — roughly equivalent to a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, or a 1.5 oz shot of spirits at 40% ABV. SipLogger's 300+ built-in drink templates are pre-configured with standard volumes and ABV percentages to help you log drinks accurately for educational BAC estimation. See our full guide to standard drink sizes.
Yes. SipLogger works entirely offline with no internet connection required. All calculations happen on your device. There are no backend servers, no cloud sync, and no data transmission — your drinking data never leaves your iPhone or iPad.
Longer reads on the formula, its accuracy, and what a standard drink is, with sources.
What formula-based estimates can and cannot tell you, and why results carry roughly ±20% variance.
The math behind BAC estimation: Widmark's model, the Watson refinement, and a worked example.
Standard drink sizes, ABV arithmetic, how definitions differ by country, and why it matters for estimation.
For iPhone and iPad, iOS 17 or later. Estimates only, for adults of legal drinking age.
SipLogger is an educational and informational tool. It does not measure blood alcohol content, estimated values vary by about ±20%, and no estimate should be used to decide whether to drive or operate machinery.