Set the scale to zero.
Place a plastic container on the scale and set it to zero again.
Fill a measuring cup with 1 cup of water.
Pour the water into the plastic container on the scale. If the scale is reading correctly, it should read 8 ounces. If the scale is not reading correctly, adjust your future measurements by the amount the scale is off, or take the scale to a professional who can adjust it for you. If you have a digital scale, it is possible to correct the calibration yourself by consulting the scale’s manual.