If you want your bathroom scale to give you an accurate measurement of your weight, you must properly set it to zero before you step onto it. Whether your scale is analog or digital, you will need to set it periodically, particularly after you've moved it into a new house, or even into a new corner of your bathroom.
Place the scale on a flat surface in your bathroom, preferably not carpet. Adjust the four corners to make them even if your model has adjusters at each corner.
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Turn the knob at the base of the scale until the needle points directly to zero. Press down on the scale with your hand and release several times; the needle should return to zero once your hand is off.
Step onto the scale until the needle comes to rest at your weight. Then, step off and verify that the needle returns to zero.
Check your scale's batteries. If they are not working, your scale will not activate when you step on it, or you may get an error message, depending on the particular model.
Set the scale on an even surface. If the corners have adjustment knobs, use those to even out the scale. Check the evenness with a level if necessary.
Depress the scale lightly with your foot, and then remove your foot. The scale should show zero. If the scale shows a different weight, consult your owner's manual. Some models feature a resetting function with a button on the scale that will let you adjust the readout to zero. Other models simply identify this discrepancy as a defect and recommend return.