Monday, 7:10 a.m.: 79.8 kg (175.9 lb). On Tuesday you step on the scale after breakfast and it says 80.9 kg (178.3 lb). Did you gain a kilo overnight? No, you weighed at a different time.
The short answer to the best time to weigh yourself: in the morning, after getting up and using the toilet, before eating or drinking, in the same clothes (or none). The hour itself is secondary. What counts is that you keep it the same every day, because only then are your readings comparable.
The morning routine that works
In the morning your body is least affected by the day. You have not eaten or drunk for hours, and the scale sits where it always sits. A fixed order saves you from deciding anew each day:
- Get up and use the toilet.
- Step on the scale before you have water, coffee or breakfast.
- Wear the same clothes every time, for example underwear only, or nothing.
- Keep the scale on a hard, level floor and do not move it around.
- Log the number right away.
Clothing counts more than most people expect: a sweater or a pair of jeans weighs a few hundred grams, and you will read that as a gain. Give the scale a permanent spot. Carpet and tile joints change the display, and a scale that lives in the bathroom one day and the bedroom the next gives you differences that have nothing to do with your body.
Why the same time beats the perfect time
Your weight moves through the day. Food, drinks, salt, training and digestion shift it, often by more than a kilo. The reasons are in Why your weight fluctuates daily. Here is an example with made-up but typical figures for one person:
| Time | Situation | Reading |
|---|---|---|
| 7:00 a.m. | after the toilet, fasted | 79.8 kg (175.9 lb) |
| 12:30 p.m. | after lunch | 80.6 kg (177.7 lb) |
| 6:00 p.m. | after work | 80.9 kg (178.3 lb) |
| 10:30 p.m. | after dinner | 81.4 kg (179.5 lb) |
Between morning and late evening there are 1.6 kg (3.5 lb), and your body fat has not changed at all. If you weigh at 7 a.m. today and at 10 p.m. tomorrow, you compare two points that have nothing to do with each other.
An evening reading is not a mistake either. If the morning is not free in your life, you can measure cleanly in the evening. The whole curve then sits about 1 to 2 kg (2 to 4 lb) higher than a morning curve, but runs parallel to it. Its slope, meaning the direction of your weight, stays the same. Only switching between times creates jumps that look like gain or loss in the data.
How often to weigh
For most people, daily is the simplest rhythm, because the habit no longer depends on a decision. You do not ask yourself each morning whether today is a weigh-in day, and the series ends up with enough points for a reliable trend. A six-month randomized trial with 91 adults by Steinberg et al. (Duke University) had one group weigh themselves daily. That group lost 13.5 lb (about 6.1 kg) on average, and 94 percent of the participants stepped on the scale at least five days a week. The study shows that frequent weighing is doable for many people and goes along with weight loss. It does not show that the time of day changes anything.
If daily weighing stresses you or you have had an eating disorder, talk to a doctor first and pick a rhythm that is good for you. Weekly at the same time beats daily with dread.
Reading the time of day in your trend
A single morning reading says little, the series says a lot. So your trend answers the question about the best hour in the end: it does not ask for a perfect measurement, only for comparable points. Trendcurve combines all weigh-ins of a calendar day into one daily value and smooths those daily values into your trend weight. By default the app uses exponential smoothing with α = 0.1. How that works is explained in Trend weight instead of daily value.
A worked example: your trend sits at 80.2 kg (176.8 lb) and you weigh 80.9 kg (178.3 lb) in the morning. The trend moves by about 0.07 kg, which is barely anything. If you weigh 81.4 kg (179.5 lb) in the evening on one odd day, it moves by about 0.12 kg. Both swings stay small. But if you switch permanently from mornings to evenings, the trend climbs by roughly a kilo over a few weeks without you gaining anything. The curve then shows a step that your schedule created.
Two settings help you keep the time. The daily reminder at a fixed time is part of the free version. Pro adds several reminder times and streak protection. Tapping the reminder opens the entry sheet directly. If your scale writes to Apple Health, Trendcurve reads the value from there. On Android it comes from Health Connect.
When your day has no free morning
Shift work, travel or small children do not always allow a fixed morning routine. The same rule applies in another form: find a recurring moment that is stable in your life.
- Shift work: weigh after you wake up, whatever the hour, and before the first meal.
- Travel: keep weighing after getting up. Other scales shift readings by a few hundred grams, so use these days for the direction, not the exact value. Mark them in the note if you like.
- Evening weighing: stay with it if it suits you, and do not switch back after a few days.
If a day is missing, do not backfill and do not guess a value. Two or three missing days barely change the trend, and with the next entry it carries on. An implausible reading, say because you stood on the scale in thick winter clothes, can be saved as ignored in Trendcurve. It stays visible in the history but does not feed into the trend.
So decide today: which moment do you take, before or after breakfast, in the bathroom or the bedroom? Write the answer down and stick to it for four weeks before you judge your trend for the first time.