Not a calorie tracker.
Calorie counting is bookkeeping; the weight trend is the result. We focus on the result and let you decide how to influence it. If you want to count calories, plenty of other apps exist for that.
The line through the noise.
Daily body weight is noisy. HackDiet shows your underlying trend, so you can see real progress and make better decisions.
€4.99 — paid once, no subscription, no in-app purchases.
iPhone, iOS 17+. Family Sharing supported.
Your weight bounces ±1 kg overnight. Most apps put that bouncing number on a chart and call it tracking.
Same data. Different question. The noise is what the scale measures; the trend is what your body is doing.
The trend is not affected by short-term shifts which mean nothing.
It will only change when there's a real shift in your weight.
A trend line is direction-agnostic.
The same noise-cancelling math works whether you want the line to drift down, hold flat, or climb.
How to start.
- 01 Weigh in. Once a day, ideally first thing in the morning. The widget logs "same as yesterday" in one tap.
- 02 See the line. HackDiet draws the smoothed trend through every reading you've ever logged.
- 03 Steer. Pick a target and a pace. The Stats view tells you whether the trend is on track — in weeks of math, not calendar dates.
Four things HackDiet is not.
Not a social app.
Your weight is between you and your scale. No leaderboards, no shared streaks, no support communities to perform for. The reward for logging is seeing the line move — that's it.
Not guesswork.
Built on a published trend-tracking methodology with verified math — not vibes, not AI, not a coach in your phone. The methodology page lays out every formula; the manual documents every value on every screen.
Not a subscription.
€4.99 once. No ads, no upsells, no in-app purchases, no recurring charge waiting to surprise you in a year. Family Sharing is enabled, so one purchase covers your Apple Family group.
HackDiet is an independent implementation of the trend-tracking methodology from John Walker's The Hacker's Diet (1991), still freely available at fourmilab.ch. We're not affiliated with or endorsed by Walker's estate.