Common Methods

• If you have a manual for your scale, read the directions. If you don't have the manual, there are several methods that should work to calibrate your scale. Try the basic methods of leveling, finding a reference weight and manual calibration. If these methods don't work, you may have to contact the manufacturer.
  
  

Level the Scale

• Make sure that the scale is on a flat, level surface. It needs to be parallel with the ground. If you don't have a leveling tool, you can get one at most hardware stores. You will need one to make sure the scale is on a level surface. If the surface is not level, it will give bad measurements because the mechanism in a scale only measures the downward component of a force. If the scale is tilted, some of the force will act in another direction. Most scales have adjustable feet that will help the leveling process.
  
  

Tare

• A scale needs to be able to recognize when there is no weight placed on it. If the scale can't be set to zero properly, it won't be able to accurately measure a weight. Digital scales can be set to zero using the "Tare" button. This method can be used to zero out receptacles. For example, if you put a beaker on the scale and zero it out, you can put a sample into the beaker and find the weight of just the sample.
  
  

Specific Weights

• The purpose of a scale is to accurately measure weight. To test that a scale is doing this properly you will need weights of known quantity. A professional calibrator will bring very accurate weights to help him calibrate a scale. You will need to do something similar. Find weights that correspond to digits on the scale. For example, if the scale measures a maximum of 10 kilograms down to a tenth of a kilogram. Find weights for each order of 10 that the scale can measure, 10 kilograms, 1 kilogram and 1/10th of a kilogram. These different weights will ensure that the scale works to the order of accuracy that you need.
  
  

Calibration

• When a scale is wrong you will need to calibrate it. You can try one of two methods. You can find a weight that you know and use that as a known quantity so the scale can have a reference. This method is similar to using the Tare button. Put on the reference weight and hit the button or the corresponding sequence of buttons to calibrate to the reference weight.
  
  The other method involves directly adjusting the scale. This similar to adjusting a digital clock. Better digital scales will allow you to use multiple reference points to ensure accuracy.