Weighing yourself regularly can help you monitor changes in your body. But it's only effective if your numbers are accurate. Crouching, standing on your tiptoes or even fidgeting can alter the reading on your weighing machine. To get an accurate measure of your weight, stand on the scale with proper posture.
Wrong Posture, Wrong Numbers
Crouching on the scale can give you an inaccurate reading. According to the book "Physics for Entertainment" by science writer Yakov Perelman, the scale may register a lower weight if you crouch down on it. Perelman explains that when you crouch it doesn't change your actual weight. But the bending movement can temporarily diminish the force that your body applies to the scale, artificially reducing the weight displayed on your scale.
Tipping the Scales
Going to the opposite extreme and standing on your tiptoes can be equally problematic. As you push down with your toes, this will increase the pressure that you are applying to the scale. As with crouching, this doesn't actually affect your weight. It will, however, falsely inflate the number on the scale.
Just Be Still!
To weigh yourself accurately, stand still and straight, maintaining proper posture on your scale. James Montagnino, vice-president of scale manufacturer Tanita, explained to Fitness magazine that you should stand on the center of the scale without shifting your weight. By standing still you will eliminate the pressure changes caused by crouching or standing. Place your scale on a flat, hard surface like a tile or hardwood floor. This will prevent you from shifting your weight on the scale. If you have a carpeted floor, Montagnino recommends placing a board between the carpet and the scale to give yourself a solid base.
Calibrate and Hydrate
Be aware that mechanical scales need to be re-calibrated on a regular basis, so they may be inaccurate if they haven't been maintained. Digital scales, which don't have moving parts, aren't prone to this problem.
If your scale measures your body fat percentage Montagnino advises against weighing yourself first thing in the morning. As he explains, you're likely to be dehydrated when you first wake up and this can give you an inaccurate body fat percentage reading.