Body Composition Scale S400.
Step on it barefoot, get 25 health metrics in seconds. Dual-frequency measurement, heart rate included, and room for 36 family members.
What it does
A scale that actually tells you something
Most bathroom scales tell you one number. This one tells you 25.
The Xiaomi Body Composition Scale S400 uses dual-frequency bioelectrical impedance to measure what is actually going on inside your body: body fat percentage, muscle mass, bone mineral content, visceral fat, protein levels, hydration, body age, and more. One measurement, one full report, delivered to your phone.
Why dual-frequency matters
Cheaper smart scales use a single electrical frequency. That gives you a rough picture. The S400 uses two frequencies simultaneously: 50 kHz to measure extracellular fluid (blood and tissue water) and 250 kHz to measure intracellular fluid (the stuff inside your cells, including muscle and fat). The combination gives a more complete and accurate result.
Xiaomi benchmarked the key body fat data against DEXA, the hospital-grade measurement standard. The correlation coefficient is 0.93 or higher. That is not the same as a DEXA scan, but it is meaningfully closer to one than most home scales manage.
What you actually see
Step on the scale barefoot, stand still for a few seconds, and you get weight, body fat percentage, and heart rate shown directly on the display. Open the Xiaomi Home app and the full 25-indicator breakdown is waiting for you.
Heart rate monitoring works the same way. Stand still, and the scale reads your resting heart rate at the end of each measurement.
One scale, whole family
The S400 stores profiles for up to 36 users and covers ages 6 to 80. It auto-recognises returning users by weight as long as nobody in the household weighs within 2 kg of each other. There is also a baby holder mode for weighing infants and a guest mode that takes a measurement without saving the data.
Battery life is around 180 days on three AAA batteries.
Worth knowing before you buy
Body fat measurement requires bare feet and a profile set up in the Xiaomi Home app. The scale works only with Xiaomi Home, not Mi Fitness or any other third-party app. This is a limitation worth knowing upfront. Measurement results are for reference only and are not a substitute for medical assessment.
