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Every fortnight, Which? free account owners are given an exclusive glimpse behind the curtain at some of our members-only product reviews.
This week, we've tested bathroom scales to find out which ones you can rely on for accurate readings. To sort the dependable from the disappointing, our experts used lab-calibrated weights and medical-grade body composition analysis to assess how consistent each scale really is.
One affordable smart scale stood out as both a Which? Best Buy and Great Value recommendation, but a cheap mechanical model from a major retailer struggled in our tests.
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At a glance: Xiaomi Body Composition Scale S400 vs Argos Home Essentials Scales
| Xiaomi Body Composition Scale S400 | Argos Home Essentials Compact Mechanical Bathroom Scales | |
|---|---|---|
| Which? test score | 86% | 32% |
| Price | SQUIRREL_TEXT_50019615 | Argos (£8) |
| Type | Smart | Mechanical |
| Weighing accuracy | ||
| Weighing consistency | N/A | |
| Body fat accuracy | N/A | |
| Body fat consistency | N/A |
Body fat consistency was measured by testers taking three back-to-back readings. Less variation in body fat percentage indicates better consistency. Weight consistency was calculated by measuring how much a 40kg test weight reading varied across multiple weigh-ins – less variation means better consistency.
Xiaomi Body Composition Scale S400 (86%, Best Buy, Great Value)
We like: Accurate readings, intuitive app, sleek design
Watch out for: App necessary to change units between kilos and pounds
If you want bathroom scales that do more than just tell you your weight, this Xiaomi model is an excellent place to start.
In our tests, it proved impressively accurate, coming close to perfect when weighing calibrated test weights, while also delivering more reliable body fat readings than rival smart scales. Just as importantly, it was highly consistent between weigh-ins, which is crucial if you're tracking changes over time.
The scales connect to Xiaomi’s easy-to-use companion app via Bluetooth, where you can view body composition metrics including body fat, muscle mass and visceral fat. We also liked the minimalist design, with the bright display cleverly hidden beneath the surface so the numbers appear to float into view when you step on.
Like all smart scales, its body fat readings shouldn't be treated as medical-grade measurements.
Still, for around £30 or less, this is a remarkably capable smart scale and an easy recommendation from our experts – especially considering some rivals cost far more and perform far worse.
For Which? members only: see our full Xiaomi Body Composition Scale S400 review.
Argos Home Essentials Compact Mechanical Bathroom Scales (32%, Don't Buy)
Available from: Argos (£8)
We like: Compact size, easy-to-read magnifying window
Watch out for: Inaccurate readings, needs frequent recalibration
These Argos mechanical scales might look like a cheap and cheerful bathroom essential, but of all the scales we tested – including smart, digital and mechanical models – these were by far the least accurate.
When weighing lab-calibrated test weights, the readings were often substantially off target, while repeated weigh-ins also produced inconsistent results.
A compact design at least means they won’t take up much room in your bathroom, but unfortunately that's one of the few positives. We also found they needed frequent recalibration, which quickly became rather frustrating during testing.
Ultimately, stepping on these scales felt more like guesswork than a reliable weigh-in.
For Which? members only: see our full Argos Home Essentials Compact Mechanical Bathroom Scales review.
Our expert says
‘Bathroom scales might seem like a basic buy that you don't need to think too hard about, but our rigorous tests show there can be huge differences in accuracy and consistency between models.
‘To separate the best from the worst, we tested each scale across a range of calibrated weights, checked how consistent the readings were over repeated weigh-ins and assessed how easy they were to use day to day. For smart scales, we also compared body composition readings against medical-grade BodPod measurements.
‘The Xiaomi scales stood out for offering highly accurate weighing at a very reasonable price. By contrast, the Argos scales struggled badly – to the point that they're a Which? Don’t Buy.
‘If you’d rather not shop around, the Xiaomi S400 is an excellent place to start. For the full results of our testing, explore our guide to the best bathroom scales.’
Jonny Martin, Which? senior researcher & writer
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