Quick guide

Your weight moves up and down every day. Most of that isn't real change — it's water, food, and timing. Steady Scale helps you see what's actually happening.

Weigh in as often as you like. The app averages each day and shows a clear trend over time, so you can tell if you're moving up, down, or holding steady.

Set a goal and it builds a simple weekly plan, shows where you're heading, and estimates when you'll get there.

Or just monitor — see your trend clearly, no goal needed. The point is awareness: when you can see what's happening, you can respond.

The chart shows four types of information, each toggleable from the legend above it:

Weigh-ins — your raw weigh-ins, shown as faint dots. Multiple readings per day are encouraged. The spread between them is the noise the app is designed to see through.

Daily avg — the average of all readings on each day. The trend line smooths these into the primary signal.

Trend — the bold blue line, and the primary signal. It smooths your daily averages into a clear direction using a 14-day rolling regression. Your check-in weights and plan are derived from this line.

Projection — your forward path when you have a goal set:

• The plan target is your target for the next check-in. It stays the same all week and updates after each check-in.
• The forecast is where your trend says you're actually heading.
• The projection line continues from the plan target at your chosen rate until it reaches your goal, with light shading that widens over time to reflect increasing uncertainty.
• The gap between the trend and the plan tells you whether you're ahead or behind.

Think about a weight you could see yourself maintaining for years, not just reaching once. A good goal is one that doesn't require heroic effort to hold, something your body can settle into with sustainable habits.

If you're losing weight, the American Heart Association considers a loss of 3–5% of body weight clinically meaningful, with 5–10% over 6 months as a strong target (Jensen et al. 2013). For a 200 lb person, that's 10–20 lb.

If you're gaining weight, focus on a target that supports your goals — whether that's recovery, athletic performance, or simply feeling better at a higher weight.

The app shows the healthy BMI range (18.5–24.9) for your height as a reference. BMI is a useful starting point, but it doesn't tell the whole story. It doesn't account for muscle mass, body composition, or individual differences, so it should be interpreted alongside other health information.

For changes of 20 lb or more, a conversation with your doctor is worthwhile before you begin. You can always adjust your goal as you learn what works for your body.

Your target rate controls two things: the plan target on your weekly check-in (how much you're aiming to change each week) and the projected goal date (when you'll arrive if you sustain that pace). A slower rate is easier to maintain and more likely to stick.

For weight loss — every major health organization converges on the same guidance; slower rates are easier to sustain and better at preserving muscle:

• 0.5 lb/wk — very gradual, easiest to sustain long-term. The NIH suggests this for lighter individuals (BMI 27–29.9).
• 1.0–1.5 lb/wk — the range recommended by the CDC and NHS. A good default for most people.
• 2.0 lb/wk — the upper limit recommended without medical supervision. Higher rates increase risk of muscle loss, nutritional deficiency, and gallstones.

For weight gain — clinical guidelines are less formalized; slower rates give better control of lean-to-fat ratio:

• 0.5 lb/wk — very gradual, best lean-to-fat ratio. Ideal if body composition matters.
• 1.0 lb/wk — a good balance of progress and body composition. A sensible default for most people.
• 1.5–2.0 lb/wk — faster progress, but expect a higher proportion of fat relative to lean mass.

If unsure, start with 1.0 lb/wk. You can adjust any time, and the projection recalculates immediately. Sources (loss): CDC · NIH/NHLBI · NHS.

Body weight routinely fluctuates by 2–4 lb (1–2 kg) from one day to the next, and most of it has nothing to do with body fat. One study estimated that 84% of short-term weight fluctuation was fat-free mass, not fat mass (Bhutani et al. 2017).

Common reasons include:

• Water balance. Your body is constantly adjusting how much water it holds. Exercise, hot weather, illness, and hydration can all make the number on the scale go up or down from one day to the next. (Bhutani et al. 2017)
• Carbohydrates. Your body stores carbohydrate as glycogen, and each gram of glycogen is stored with several grams of water. Eating more or fewer carbohydrates than usual can change your weight by a few pounds without changing body fat. (Fernández-Elías et al. 2015)
• Food and digestion. Food and drinks have weight too. A large meal, the timing of your last meal, or whether you've been to the bathroom yet can all move the scale by a pound or two.
• Hormones. Hormonal changes can temporarily increase water retention. For many women, this is most noticeable in the days leading up to their period. (White et al. 2011)

These daily fluctuations are normal, but they can make it difficult to know whether your weight is actually changing. Steady Scale averages multiple readings per day and fits a trend over 14 days to separate short-term noise from longer-term movement. Averaging reduces intra-day noise, while the trend model reduces inter-day noise, making the underlying direction of your weight easier to see.

The trend is a 14-day rolling Ridge (L2-regularized) regression, chosen after testing several models (ordinary least squares, weighted regression, exponential smoothing, and Ridge) across different windows and forecast horizons, on both real and simulated data. It gives stable estimates without overreacting to noisy days.

See the Science page for the full method: why Ridge, the bias–variance tradeoff, and how we chose the window.

Your measurements are stored on your device and automatically backed up to your iCloud account. No data is sent to our servers or any third party.

If you lose or replace your phone: sign into the same Apple ID on your new device, download Steady Scale, and the app will find your backup and offer to restore it.

You can export your data any time. It's always available, even without a subscription.

iCloud backup is on by default. Every time you log a measurement, your full dataset is backed up in the background.

What it doesn't do yet: sync between multiple devices in real time. Each device keeps its own copy. Multi-device sync is something we're considering for a future update.

Steady Scale is an awareness and measurement tool, not a diagnostic device. It does not diagnose, treat, or prescribe.

The trends and forecasts shown in the app are statistical estimates based on the measurements you enter, not personalized health recommendations.

Talk to a qualified healthcare professional before starting, modifying, or stopping any diet, exercise, or weight-management program. This is especially important if you are pregnant or nursing, have a history of disordered eating, have a medical condition that affects weight or appetite, or are under the age of 18.

If your relationship with food, weight, or your body ever feels difficult, support is available.

Alliance for Eating Disorders Awareness
1-866-662-1235 · allianceforeatingdisorders.com

Outside the US? Search for eating disorder or mental health support in your country. Your doctor is always a good first step.