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This page describes products and general use; it is not medical advice.
An infant scale weighs a baby lying on a tray; it does not measure length. Length is measured on a separate device, a pediatric length board (infantometer), and standing height on a stadiometer. This page separates the three, shows how US regulation classifies patient scales, and lists the use and calibration basics the American Academy of Pediatrics (AAP) publishes.
Who uses it: pediatric clinics and other settings that record infant body weight, and the staff and buyers who equip them.
What an infant scale is
An infant scale is a scale built for weighing a baby lying on its back on a tray, so the body weight can be read and recorded. The AAP lists “infant scales, beam-balance scales, and digital scales” as the scales used for body weight in its anthropometric measurement guidance (checked 2026-10-30).
Infant scale vs infantometer (pediatric length board)
These are different instruments that answer different questions. The scale gives weight. The length board gives recumbent length, the measurement taken lying down.
| Device | Measures | Key difference |
|---|---|---|
| Infant scale (tray style) | Body weight | The infant lies on the tray, centered, touching nothing but the tray (AAP). |
| Pediatric length board (infantometer) | Recumbent length | A board with a movable footboard and a fixed headboard; the AAP says length devices should be calibrated and accurate to 0.1 cm. |
| Stadiometer | Standing height | Used standing; see the stadiometer guide for how it differs from the infantometer. |
Types of scale used for infant weight
| Type | Typical use | Source |
|---|---|---|
| Infant scale | Body weight | AAP, Anthropometric Measurements |
| Beam-balance scale | Body weight | AAP, Anthropometric Measurements |
| Digital scale | Body weight | AAP, Anthropometric Measurements |
The AAP names these three types for body weight and does not rank them.
How infant scales are regulated in the US
US federal regulation defines a patient scale in 21 CFR 880.2720 as “a device intended for medical purposes that is used to measure the weight of a patient who cannot stand on a scale.” The definition includes devices where the patient is placed on the scale platform to be weighed, and the device may be mechanical, battery-powered or AC-powered. The regulation classifies patient scales as Class I (general controls) and exempts them from premarket notification (510(k)), subject to the limitations in 21 CFR 880.9 (checked 2026-10-30, Cornell LII). The regulation does not use the words “infant scale”, so a manufacturer’s labeling and regulatory listing is the place to confirm how a specific model is classified. For how 510(k) differs from other pathways, see 510(k) vs PMA.
Safe use and handling basics
These points come from the AAP guidance on weighing infants (checked 2026-10-30) and are general, not individual advice.
- Scales must be regularly calibrated to maintain accuracy. For calibration concepts see calibration interval and calibration certificate.
- Weigh the infant with clothing and diaper removed. A clean diaper is acceptable if the scale is first zeroed with the weight of the clean diaper.
- Zero the scale before the infant is placed on it.
- The infant lies on the back, centered on the tray, touching nothing but the tray. Then read and record the weight.
Recording length on the length board
The AAP describes recumbent length as a two-person measurement: one person holds the head against the headboard while the other flattens the knees and holds the ankles with the feet flat on the footboard. Length is recorded to the last completed 0.1 cm. The CDC/HRSA growth chart training module (University of Washington, checked 2026-10-30) adds that both legs should be fully extended with the toes pointing upward and the feet flat against the footpiece.
Common mistakes
Each of these is the opposite of a step in the AAP guidance above.
- Weighing in a diaper without first zeroing the scale to the weight of the clean diaper.
- Skipping regular calibration.
- Letting the infant touch something other than the tray, or placing the infant off-center.
- Using a single person to take recumbent length when the guidance describes two.
Frequently asked questions
What is the difference between an infant scale and an infantometer?
An infant scale measures weight; an infantometer, also called a pediatric length board, measures recumbent length. They are used in the same visit but are separate devices.
Does an infant scale need calibration?
Yes. The AAP states that scales must be regularly calibrated to maintain accuracy.
Is an infant scale a regulated medical device in the US?
A scale intended for medical purposes to weigh a patient who cannot stand is a patient scale under 21 CFR 880.2720: Class I and exempt from 510(k), subject to the limitations in 21 CFR 880.9.
Can an infant be weighed in a diaper?
The AAP says the infant is weighed with clothing and diaper removed, or in a clean diaper if the scale is first zeroed with the weight of the clean diaper.
Related pages
See the pediatric clinic supply checklist for where the scale and length board sit among clinic equipment, and the exam table guide for the other fixed equipment in the room.
Sources
- American Academy of Pediatrics, Anthropometric Measurements, checked 2026-10-30.
- 21 CFR 880.2720, Patient scale, Cornell Legal Information Institute, checked 2026-10-30.
- University of Washington, CDC/HRSA growth chart training, module 5, checked 2026-10-30.
