Whether it’s bananas, olives, potato salad, or cereal, many products are priced according to their weight. That weight is likely determined on a scale tested and certified by a specially trained state or local inspector. Weights and measures underpin approximately half of the United States gross domestic product (GDP), so it’s important to get things right.

To ensure you are getting the correct amount of product at the supermarket, inspectors routinely examine and certify scales for accuracy. To do that, they carry what they call “field standard weights,” which are designed to be used outside of their state or local laboratory. For instance, the field standard weights for inspecting grocery scales usually contain increments of 1 lb, 2 lb, and 5 lb so inspectors can test a scale to full capacity (usually 30 lb for most grocery scales), as well as smaller weights to ensure that the scale is accurate at smaller loads.

 …