Dual-frequency measurement and accuracy compared to a DEXA scan: This is Xiaomi’s new feature-packed smart scale

This is one of those gadgets that basically didn’t change for years. Xiaomi decided to shake things up in two ways: it removed the metal electrodes you had to hit with your feet, and instead of an energy-saving LED display it put a proper color panel on the scale. The Mijia Body Composition Scale S400 Pro is currently only listed on the global website, but it’s already clear that this will be the most feature-packed scale the brand has.

A scale that no longer has electrodes

The biggest change is under your feet. Traditional scales use metal electrodes only on part of the surface, and if you don’t step on them exactly, body composition measurement can fail or be inaccurate. The S400 Pro has instead an entire 300 × 300 mm surface made of tempered glass with a conductive ITO layer — you can simply step anywhere. According to Xiaomi, it’s also enough to read even European shoe size 48.

The glass is also a design element — a dark gray mirrored surface with a metal Mijia logo in the center, rounded edges, and silicone feet. In terms of size, it’s bigger than we’re used to, and that’s intentional here: a larger platform means a steadier stance and more accurate measurements.

Dual-frequency measurement and 25 parameters

The scale uses bioimpedance at two frequencies at once. The lower frequency 50 kHz measures fluid outside the cells, while the higher 250 kHz measures fluid inside the cells — from the difference, it can estimate the fat and muscle ratio more accurately than budget scales with only one frequency. Xiaomi states that the correlation with a reference DEXA scan exceeds 0.93.

The result is 25 indicators — besides weight, there’s BMI, body fat percentage, muscle mass, water content, proteins, visceral fat level, and even heart rate. You can use the scale with up to 36 profiles for ages 6 to 80, and it can weigh small items, luggage, or a child in your arms too, since the range starts at 100 grams. Still, keep in mind what applies to every bioimpedance scale: these are estimates, not medical measurements — and what they tell you most is how things trend over time, not a single specific morning.

Color display and memory for 160 measurements

3.5-inch TFT display is the second big change. Instead of a few segments, you can see more data at once, trends, and the on-screen guidance that walks you through the measurement. You can also customize what appears on the display through the app — choose which values to show and adjust the brightness.

The scale remembers 160 measurements, so nothing gets lost if you don’t have your phone with you; once you connect, everything syncs. It works via Bluetooth LE 5.1 and connects even when the display is off — you don’t have to step on the scale first. If you have a Bluetooth gateway at home, the data uploads to the cloud completely without a phone. It’s powered by four AAA batteries, and with three weigh-ins per day it should last 150 days.

One thing that’s annoying: a third app

And now the worse part. On the Xiaomi product page’s FAQ, Xiaomi explicitly states that the scale can be connected exclusively to the Xiaomi Home app, and other apps are not supported. It sounds like a minor detail, but in practice it means a split history: if you wear a Xiaomi band or smartwatch, your steps and sleep live in the Mi Fitness app. Older Xiaomi scales collected data in Zepp Life — and this scale will be the third app in line.

Xiaomi is creating this mess itself, and with a product meant to track a long-term trend, a fragmented history is the real problem. If you already use Xiaomi Home to manage your smart home, there’s nothing new to install. But if you’re used to Mi Fitness, expect the weight data to be in a different place than your fitness data.

How is it different from the base S400 model?

Xiaomi also offers the cheaper Body Composition Scale S400 (model MJTZC01YM), and the differences are specific. The Pro version has a color TFT display instead of LED, a more precise weighing segment (0.05 kg vs 0.1 kg), a newer Bluetooth 5.1 instead of 5.0, and it’s powered by four batteries instead of three. In return, it’s a bit heavier (1.65 kg vs 1.45 kg) and about a millimeter thicker.

Price and availability

In China, the scale is sold for an amount that is equivalent to under €30. Xiaomi hasn’t announced the official EU availability or price yet — for now, the model is only on the global site, which is usually the first step before it comes to our markets.

For now, you can only get it through Chinese e-shops, like for example AliExpress, where resellers offer it. However, note that it’s the China version, and in the app you need to set the region to Mainland China.

Factor in shipping and taxes roughly to about around €80. If you don’t want to wait, the alternative is the base S400 model, which is commonly sold in Europe and costs less.

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