You reached your goal weight of 80 kg (176 lb). On Monday the scale says 80.9 kg (178.4 lb), on Thursday 79.6 kg (175.5 lb), and each number feels like a verdict. Nobody holds a single number to the decimal, but you can hold a band around it. The maintenance corridor in Trendcurve draws that band around your goal weight. As long as your trend weight stays inside it, you are maintaining, whatever the daily readings do.
Why one number is a poor target for maintenance
Your weight moves from day to day by more than a maintenance plan can resolve. Salt, digestion, training and sleep shift the reading, as described in why your weight fluctuates daily. While you lose weight, this is easy to overlook because the curve has a direction. While you maintain, it has none, and every spike upward looks like the start of a regain.
A corridor gives that scatter a frame and answers a practical question: when is it worth changing something? While the trend sits inside the limits, the answer is: not yet. Once it leaves them, you have a clear reason to look at what changed over the past few weeks.
How to set up the corridor
The corridor belongs to maintenance mode. You get there in two ways: when you reach your goal, the goal celebration offers a button to start holding your weight, or you change your goal type to "Maintain" yourself. After that, a corridor card appears in the Goal tab. It only shows up in maintenance mode.
The default is ±1.5% of your goal weight. You can choose any width from ±0.5% to ±5%, or enter a fixed amount instead. The lower bound never falls into the underweight range, even if the percentage or amount would reach further down. Someone who has lost weight cannot build a corridor that lets them drift toward underweight.
A worked example with an 80 kg goal
The limits depend on the setting:
| Setting | Lower limit | Upper limit |
|---|---|---|
| ±0.5% (±0.4 kg) | 79.6 kg (175.5 lb) | 80.4 kg (177.3 lb) |
| ±1.5% default (±1.2 kg) | 78.8 kg (173.7 lb) | 81.2 kg (179.0 lb) |
| ±5% (±4 kg) | 76.0 kg (167.6 lb) | 84.0 kg (185.2 lb) |
| fixed amount ±1 kg | 79.0 kg (174.2 lb) | 81.0 kg (178.6 lb) |
The trend moves far more calmly than the daily readings, but it moves. A narrow corridor reacts sooner, a wide one allows more regain before anything happens. If you want early signals, go narrower. If small wobbles make you anxious, go wider. The default of ±1.5% is a reasonable middle for starting out.
The size of the percentage also changes with your body weight: at a 120 kg (265 lb) goal, ±1.5% is already ±1.8 kg (4.0 lb), at 55 kg (121 lb) it is only ±0.8 kg (1.8 lb). A fixed amount treats both the same.
Reading the corridor in your trend curve
In the chart, the corridor sits as a band behind the curve, and the same band shows in the status display. Both are free in Trendcurve. Daily weigh-ins may jump out of the band. What counts is the trend line, which is smoothed from those weigh-ins. How that smoothing works is covered in trend weight instead of daily weight.
After a salty dinner the scale shows 82.0 kg (180.8 lb), above the upper limit of 81.2 kg. Your trend, however, sits at 80.6 kg (177.7 lb), in the middle of the band. You do nothing and weigh in tomorrow as usual. Going by the daily number alone, you would have cut a meal for nothing.
On iPhone, the widget also shows your position in the corridor while you are in maintenance mode.
With Pro you also get the corridor history. It counts the days your trend stayed inside the corridor, shows the share over 30 and 90 days and names your longest streak. As a sum: if the trend sat inside the band on 27 of 30 days, the history shows 90%.
The early warning: when Trendcurve speaks up
The early warning is also Pro. It sends a notification and shows a banner in the Today tab when one of two conditions applies:
- Your trend has left the corridor.
- At your current weekly rate, your trend would leave the corridor within 14 days.
Each direction triggers at most one alert in 14 days. Tapping the notification opens the Goal tab.
An example with the same 80 kg goal and ±1.5%, so an upper limit of 81.2 kg: your trend stands at 80.8 kg (178.1 lb) and the weekly rate is +0.25 kg (0.55 lb). In 14 days that adds up to 80.8 + 0.5 = 81.3 kg (179.2 lb), above the limit. Trendcurve alerts you even though the trend is still inside the band today.
That gives you roughly two weeks of lead time. It is enough to look at last month's portions, your daily movement or a new habit without having to cut back in a hurry. The weekly rate comes from the last 14 trend values, not from single days.
Limits and what stays free
The corridor has limits you should know:
- It judges the trend, not the body. It does not tell you whether a change is fat, water or muscle.
- The trend lags behind daily weigh-ins. A sudden rise shows up only after a few days.
- The early warning extends the current rate in a straight line. After a week of holiday or illness the rate can look steeper than it stays. Treat the alert as a prompt to look, not as a forecast.
- After an alert, the warning rests for that direction for 14 days. During that time you read the trend yourself in the chart.
If you gain or lose weight without a clear reason, talk to a doctor. Trendcurve is not a medical device.
On the split: the band in the chart and the status are free, the corridor history and the early warning belong to Pro. The free version is enough to start, because it shows the most important thing, where your trend sits relative to your goal.
Set the corridor to the default of ±1.5% first, let it run for four weeks and adjust the width only after you have seen where your trend actually moves.