Weighing

Weighing is the process of determining the quantity of matter in an object, commonly expressed as mass or weight. In physics, mass is the intrinsic amount of matter in an object, while weight is the force exerted on that mass by gravity. Because gravity varies slightly across the planet, weight can differ with location even for the same object, whereas mass remains constant.

The principal instruments for weighing are balances and scales. Mechanical balances, such as two‑pan beam balances, compare an object's mass against known reference weights. Electronic scales use sensors such as load cells, strain gauges, or capacitive elements to convert a force into an electrical signal that is displayed as mass or weight. Weighing can be direct (placing the item on a scale) or indirect (inspecting weight changes, or calculating mass from other measurements). For irregular objects, buoyancy corrections may be needed when measurements occur in fluids.

Key concepts in weighing include tare, gross, and net weight. Tare weight accounts for the mass of containers or packaging, allowing determination of net content. Units of mass include kilograms and grams in the metric system, with pounds and ounces commonly used in some other regions. Calibration and traceability are essential for accuracy, often involving reference weights that are certified to national or international standards.

Applications span commerce, science, medicine, and industry, where precise and reliable mass measurements are required. The history of weighing encompasses ancient balance scales and the later development of spring and electronic scales, reflecting ongoing improvements in precision, speed, and automation.