Correct Techniques for Measuring Human Height

How tall are you? The NASA Quest website explains that many people are measurably taller in the morning than later in the day. This is because most people sleep at night and the vertebrae in the disks separate while the body is lying down. Height can also vary depending on the methods of measurement.

Correct measuring techniques ensure the most accurate possible height measurements.

Measuring Standing Height

According to the Center for Disease Control, to obtain an accurate height measurement, begin by removing bulky clothing, including thick-soled shoes and hair ornaments. Stand against a wall facing outwards and look straight ahead. Your head, shoulders, rear end and heels should touch the wall. Get a friend to gently press a ruler or any flat stick down on the top of your head; then mark the spot where the ruler touches the wall with a pencil. Step away from the wall and use a tape measure to record the distance from the floor to the mark, without rounding up fractions of centimetres or inches.

Measuring Height Lying Down

If the person you're measuring is unable to stand, you can take his height while he is lying down, according to University College London. Ask him to lie on his back in light clothing or undergarments, without shoes or hair ornaments. Position his body as flat as possible with his feet together and the heels touching the back plate of the instrument used to take the measurement. Take the measurement from the top of the head, without rounding up.

Height Measurement Variations

According to the Osteoporosis Society of Canada (OCS), height measurements taken more than a year apart can vary by 3 centimetres because of measurement error. OCS recommends taking three different measurements, and averaging the results to achieve the most accurate measurement.

For those with legs of different lengths, make the measurement while the person is standing on the longer leg, states University College London. The longer leg should be noted and the same leg used for all future measurements.

Measuring Seated Height

In some cases, measuring the proportion of the trunk in comparison with a separate measurement of overall height can have clinical relevance. Examples include assessing cases of achondroplasia, which is the most common form of dwarfism, along with other forms of short stature, as well as evaluation after irradiation of the spine.

According to University College London, a stadiometer or a ruler attached vertically to a chair or a box placed against a wall is commonly used for measuring seated height. The subject sits on the box or chair with her feet flat on the floor and her back pressed against the ruler while looking straight ahead. The clinician measures the distance from the floor to the top of the subject's head. The clinician then subtracts the height of the chair or box from the total height to obtain the trunk measurement.