TL;DR
- Weight: accurate. Consumer smart scales were within a median 0-0.3 kg of the hospital reference for body weight.[1]
- Body fat: not accurate enough to trust as a number. The same scales, a Withings among them, misread fat mass by a median 2.2-4.4 kg against DEXA.[1]
- The method, not the brand, sets the error. Withings, Renpho and Eufy all use BIA, which reads body water and estimates fat from it.[4][5]
- Trends are rough, too. BIA underestimated six-month body-fat change by about 3 points versus DEXA.[3] Eufy no longer sells scales on eufy.com in the US.[6]
How accurate is smart scale body fat? Accurate for weight, not for body fat: in independent studies consumer BIA scales, including a Withings model, missed DEXA by several kilograms of fat mass, and no brand escapes that because the error comes from the method.[1][2] This guide compares what Withings, Renpho and Eufy offer and what the peer-reviewed BIA-versus-DEXA studies say they can and cannot do. Verified 2026-10-11.
How close does a smart scale get to DEXA?
BIA sends a small current through the body and estimates fat from electrical resistance, which depends on body water as much as on fat. In a French hospital study, three consumer scales (Tefal Body Partner, Terraillon DietPack and Withings Body Cardio) were checked against DEXA in about 50 patients each. Weight was close (median error 0-0.3 kg), but fat mass was off by a median 2.2, 4.4 and 3.7 kg, with wide spreads between people.[1]
The error grows at the extremes. A Tanita foot-to-foot BIA scale overestimated body fat by about 10 percentage points on average in 197 young people with overweight or obesity, with individual errors near 24 points.[2] In 189 adults in a weight-loss trial, BIA underestimated body fat by 4.6-5.1 points at baseline, with 95% limits of agreement spanning about 14-15 points.[3]
How do Withings, Renpho and Eufy compare?
| Spec | Withings Body Comp | Renpho MorphoScan | Eufy smart scales |
|---|---|---|---|
| Price (US) | $229.95[4] | $179.99 list[5] | No longer sold by eufy[6] |
| BIA type | Two-frequency[4] | 8-electrode, dual-frequency[5] | Foot-to-foot |
| Segmental (by limb) | No; reserved for Body Scan[4] | Yes, 5 body parts[5] | No |
| Metrics | Fat, muscle, water, visceral fat, vascular age[4] | 50+ in app[5] | n/a |
| Body fat vs DEXA | BIA-class error of several kilograms or points for all three[1][2] | ||
What do you actually pay more for?
The Withings Body Comp uses two-frequency BIA and reports body fat, muscle, water, visceral fat and extras such as vascular age; Withings reserves segmental analysis for the $499.95 Body Scan. The Body Comp lists at $229.95.[4] Renpho's MorphoScan ($179.99 list, on sale for $169.99 on 2026-10-11) is the most capable on paper, with 8 electrodes, dual-frequency BIA and fat and muscle estimates for five body parts.[5] Neither feature has been shown to close the gap to DEXA; handles mainly add a current path through the upper body.
Is Eufy still selling smart scales?
Not directly in the US. eufy.com no longer lists smart scales, and its smart-scale collection page redirects away (checked 2026-10-11).[6] Units may remain on third-party retailers without maker support, so Withings and Renpho are the safer buys. We have not run our own DEXA comparison on any of these scales; every accuracy figure here comes from independent peer-reviewed studies.
How should you use a body-fat scale?
- Trust the weight, and read its trend across weeks, not days.
- Standardise body-fat readings: same time of day, after the bathroom, before eating or drinking, so hydration varies less.
- Read monthly direction, not weekly decimals. Even change estimates carried a 3-point bias against DEXA in a six-month trial.[3]
- Use DEXA when you need a true body-fat figure for a meaningful decision.
The verdict: pick the Renpho MorphoScan for the most metrics and segmental estimates for the money, the Withings Body Comp for its app ecosystem and cardiovascular extras, and avoid buying an Eufy scale without maker support. Do not expect DEXA-grade body fat from any of them. To work with the numbers, use the Body Fat Percentage Calculator, and for how scales, calipers and DEXA compare read skinfold calipers vs BIA scale vs DEXA.
Verified 2026-10-11. Every accuracy figure is sourced to a named peer-reviewed validation study; prices and availability change without notice.
Frequently asked questions
Is Withings, Renpho or Eufy the most accurate for body fat?
None is accurate enough against DEXA to trust as an absolute number. All three use bioelectrical impedance (BIA); in a hospital study three consumer scales, one a Withings, misread fat mass by a median 2.2 to 4.4 kg against DEXA.[1] The brand mainly changes how many electrodes and metrics you get.
How far off is a smart scale from a DEXA scan?
Typically several kilograms of fat mass or several body-fat percentage points. A foot-to-foot BIA scale overestimated body fat by about 10 points on average in youth with obesity, with single errors near 24 points,[2] and in adults BIA's 95% limits of agreement with DEXA spanned roughly 14-15 points.[3]
Can a smart scale track body fat changes?
Roughly, not precisely. In a six-month weight-loss trial, BIA underestimated the change in body fat by about 3 points on average compared with DEXA.[3] A scale can show direction over months under fixed conditions, but small weekly changes are within its noise.
Is the Eufy smart scale still available?
Not from eufy in the US: eufy.com no longer lists smart scales, and its smart-scale collection page redirects away (checked 2026-10-11). Units may still be sold by third-party retailers, without direct maker support.[6]
References
- 1 Accuracy of Smart Scales on Weight and Body Composition: Observational Study (Frija-Masson et al.) — Tefal, Terraillon and Withings Body Cardio vs DEXA — JMIR mHealth and uHealth, 9(4):e22487 (2021)
- 2 Body fat assessment in youth with overweight or obesity by an automated bioelectrical impedance analysis device, in comparison with the dual-energy x-ray absorptiometry (Samouda et al.) — Tanita BC-532 vs DEXA — BMC Endocrine Disorders, 22:195 (2022)
- 3 Percentage of body fat assessment using bioelectrical impedance analysis and dual-energy X-ray absorptiometry in a weight loss program for obese or overweight Chinese adults (Li et al.) — PLoS One, 8(4):e58272 (2013)
- 4 Withings Body Comp product page ($229.95; two-frequency BIA; segmental analysis reserved for the $499.95 Body Scan) — Withings (2026)
- 5 RENPHO MorphoScan body composition scale ($179.99 list; 8-electrode dual-frequency BIA, segmental fat and muscle, 50+ metrics) — RENPHO (2026)
- 6 eufy smart scale collection (now redirects away; eufy no longer sells smart scales on eufy.com) — eufy (2026)