Is the Xiaomi Scale 2 (S400) actually accurate for body fat?
Worth it, if you want a family trend tracker, not a clinical scale
Why the number on a normal scale doesn't tell you much
You step onto a bathroom scale first thing in the morning, watch the number settle, and feel it tell you almost nothing about what actually changed in your body. That single figure doesn't say whether you lost fat or muscle, whether last night's salty dinner is just water weight, or whether the diet is doing anything at all. It's why a lot of people end up reading a xiaomi scale 2 review before buying one: the promise of a body fat percentage feels like the missing piece. The real question is whether a scale this cheap can actually tell you that, or whether it's just guessing with better graphics.
How the Xiaomi scale 2 actually measures body fat
The S400 works on bioelectrical impedance analysis, the same principle used in clinical body composition tools, scaled down for a bathroom floor. Step on with bare feet and it sends a current so small you can't feel it, up one leg and down the other. Fat resists that current more than lean tissue does, because muscle holds more water and water conducts electricity easily. The scale measures how much resistance it meets, then runs that number through algorithms built from your height, age, sex and weight, entered once in the companion app, to estimate the twenty five metrics on the label: body fat, muscle mass, visceral fat, bone mass, water percentage and more. That's also why the number shifts day to day even when nothing meaningful has changed. Hydration changes resistance. A workout raises blood flow to your legs and skews the reading. Stepping on it right after a shower, with wet feet, throws it off entirely. None of that is a malfunction, it's what BIA is: an estimate built from electrical resistance and population averages, not a direct measurement of fat cells. The app's real value shows up over weeks, not on any single morning, because it graphs the trend line and smooths out the daily noise. With thirty six user profiles and automatic recognition, it can track a whole household's separate trend lines too, which a single-person scale can't do.
So you're not buying a lab-grade body fat number, you're buying a Tuesday-versus-last-Tuesday trend line for a household. The absolute figure matters less than whether it's moving the direction you want, and for that, consistency in when and how you weigh yourself matters more than the device's raw precision.
Who the Xiaomi scale 2 is for, and who should skip it
Worth it if
- you want to track body composition trends over months rather than a single accurate reading
- multiple people in your household want their own profile and history
- you're willing to weigh yourself at a consistent time of day for reliable trends
Skip it if
- you need clinically accurate body fat percentages for medical or athletic purposes
- you want one definitive number rather than a moving trend line
- you won't install or regularly use the companion app
If you need clinically accurate body fat numbers for medical or athletic decisions, this isn't that scale.
The Xiaomi scale 2 review verdict
If you want a rough, running sense of how body composition is trending over months, shared across a family, this is a quiet yes. If you need clinically accurate body fat numbers for a medical or athletic decision, this isn't that scale, and honestly no home scale is.
The problem this solves is that vague, information-less number that used to leave you guessing what actually changed. Day one looks like everyone in the house stepping on once, syncing to their own profile, and watching a few honest trend lines start to form instead of a single mystery figure. With over 2,500 ratings behind it, buyers consistently describe it as a satisfying way to watch weight and body fat shift over weeks, which is exactly the job this scale is built for.
Amazon shoppers rate it 4.4 out of 5 across 2,540 ratings. That is their number, not ours.
This is a product review, not medical advice. We research how products work and whether they earn their price; we don't test them clinically and nothing here is a treatment recommendation. For anything that affects your health, talk to a qualified professional first.
Before you go
Is the Xiaomi body composition scale 2 accurate?
It's accurate at tracking trends over time, but like every home bioelectrical impedance scale, its single-reading body fat number is an estimate, not a clinical measurement.
What are common issues with the Xiaomi scale?
Readings can shift day to day based on hydration, recent exercise or wet feet on the plates, which is normal behavior for impedance-based scales rather than a defect.
What is the difference between MI scale 2 and S400?
The Mi Body Composition Scale 2 was Xiaomi's earlier body composition scale, while the S400 is the newer version behind most 'Xiaomi scale 2' searches now, with an updated design, LED display and an expanded 25-metric readout through the Xiaomi Health app.
What is the most accurate smart scale on the market?
No consumer bioelectrical impedance scale matches clinical tools like a DEXA scan; the most useful ones, including this one, are best judged on trend consistency rather than absolute accuracy.
By the numbers
earn an unconditional yes at full priceOut of 300 health & personal care products we have reviewed. This one is a yes with a condition attached.
Verdict datasetQuestion indexCC BY 4.0
Full spec sheet
| Special Features | Body Fat, Bodyweight, Smart, Tare Function |
|---|---|
| Display Type | LED |
| Weight Capacity Maximum | 150 kg |
| Form Factor | floor scale |
| Weigh Scale Type | Floor Scale |
| Measurement Type | Digital |
| Color | white |
| Material Type | Glass Plastic |
