Scalin
True weight
A smoothed trend line (EWMA, α 0.1) instead of daily whiplash — and your real weekly rate, up or down.
iPhone · Apple Watch · Widgets
Water, salt, yesterday's dinner — the number jumps 400 g and the whole week feels wasted. Scalin ignores that number and tracks the line underneath it.
+0.9 kg overnight? You ate salt, not fat. Sit down.
True weight
Sixty mornings of readings. Every one of them accurate, and every one of them useless on its own.
One line underneath them: an exponentially weighted average of your own weigh-ins — the Hacker's Diet method. It only moves when you actually do.
What it does
A smoothed trend line (EWMA, α 0.1) instead of daily whiplash — and your real weekly rate, up or down.
Fourteen flat days is a plateau, not a failure. Scalin names it instead of letting you guess.
A range to a date, never a fake single number. If the data can't say, it says so.
Every 5%, every new low in the window, every round number. Once each — no confetti loops.
Spin the ruler or type the number. Missed a morning? Add it later. Weekends never break your streak.
Your whole history imports on day one and every weigh-in writes back. Smart scales land in Scalin on their own.
The character
One line a day, tied to what your weight actually did. The jokes are aimed at the scale, at salt and at Mondays — never at your body. A line that doesn't land: mute it, and it never comes back.
Supportive
Down 0.2 this week. Slow is still the direction you asked for.
Snarky
Fourteen days flat. Bold of you to keep weighing in.
Merciless
The trend hasn't moved. The scale isn't the thing that's broken.
Wrist & home screen
Log with the Digital Crown, read the trend on your wrist, keep it on a complication. Health is the transport — nothing to pair.
Home and Lock Screen widgets show the arrow and the change. Your actual weight stays off the screen unless you turn it on.
The morning reminder. That is the entire notification budget, forever.
Privacy
Scalin has no backend for your data. Weigh-ins live in the app's container on your device and sync through your own iCloud — we never receive them, because there is nowhere for them to go. Anything read from or written to Apple Health stays on the device too.
The app measures how it is used — screens opened, features tapped, crashes — through Google Analytics for Firebase, so we know what to fix. That stream carries no weight, no weigh-in and no health data. Ever.
Scalin never asks your height, never calculates a BMI, and never tells you what to eat. It tracks weight, and it is honest about it.
The trend is a smoothing of your own measurements — not a medical device, a diagnosis or a prediction.
Scalin Pro
Pro unlocks the trend line, the weekly rate, forecasts, the character and the widgets. Without it you keep your log and the raw chart.
$44.99
per year · 7 days free
$5.99
per week · 7 days free
Payment is charged to your Apple Account at confirmation of purchase. The subscription renews automatically unless it is cancelled at least 24 hours before the end of the current period. Manage or cancel it in your Apple Account settings. See the Terms and the Refund Policy.