Digital pocket scales are often calibrated using special weights. However, these weights are expensive. It is possible to use household items with a known mass, such as nickels, to calibrate a scale.
According to Do It Yourself, digital pocket scales can be calibrated using nickels because each nickel has a known mass of 5 grams. Several steps are involved to calibrate the scale. First, clean it with water and then acetone or ethanol. After the scale dries, reset it to zero. Next, find the expected calibration mass of the scale, often found in the user manual. After this gather a certain number of nickels to meet the target mass; as each weighs 5 grams, divide the target mass (in grams) by 5 to determine the number of nickels required. Clean and dry them to avoid alterations in mass. Finally, place the nickels onto the scale, and press the calibration button to let the scale perform the calibration.