Open Access Highly Accessed Research article

Accuracy and consistency of weights provided by home bathroom scales

Meredith Yorkin1, Kim Spaccarotella1, Jennifer Martin-Biggers1*, Virginia Quick2 and Carol Byrd-Bredbenner1

Author Affiliations

1 Department of Nutritional Sciences, Rutgers, The State University of New Jersey, 26 Nichol Avenue, Davison Hall, 08901, New Brunswick, NJ, USA

2 Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health & Human Development, National Institutes of Health, 6100 Executive Boulevard, 20892, Bethesda, MD, USA

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BMC Public Health 2013, 13:1194  doi:10.1186/1471-2458-13-1194

Published: 17 December 2013

Abstract

Background

Self-reported body weight is often used for calculation of Body Mass Index because it is easy to collect. Little is known about sources of error introduced by using bathroom scales to measure weight at home. The objective of this study was to evaluate the accuracy and consistency of digital versus dial-type bathroom scales commonly used for self-reported weight.

Methods

Participants brought functioning bathroom scales (n = 18 dial-type, n = 43 digital-type) to a central location. Trained researchers assessed accuracy and consistency using certified calibration weights at 10 kg, 25 kg, 50 kg, 75 kg, 100 kg, and 110 kg. Data also were collected on frequency of calibration, age and floor surface beneath the scale.

Results

All participants reported using their scale on hard surface flooring. Before calibration, all digital scales displayed 0, but dial scales displayed a mean absolute initial weight of 0.95 (1.9 SD) kg. Digital scales accurately weighed test loads whereas dial-type scale weights differed significantly (p < 0.05). Imprecision of dial scales was significantly greater than that of digital scales at all weights (p < 0.05). Accuracy and precision did not vary by scale age.

Conclusions

Digital home bathroom scales provide sufficiently accurate and consistent weights for public health research. Reminders to zero scales before each use may further improve accuracy of self-reported weight.

Keywords:
Body weight; Body mass index; Validity