The permissible or legally known weight of an empty vehicle or container is referred to as tare weight. The net weight of a cargo is calculated by subtracting the tare weight from the gross weight. The cargo charges are determined based on this calculation.

The word tare comes from the Middle French word tare, which means "wastage in goods, deficit, defect" (15th century), from Italian tara, from Arabic ar, which means "item subtracted or rejected," and taraha, which means "to reject."

This can be useful in calculating the cost of goods carried for tax purposes or tolls associated with barge, rail, road, or other transportation, particularly if the toll varies with the value of the commodities carried (e.g., tolls on the Erie Canal). Tare weight is frequently shown on the sides of railway carriages and transport vehicles to aid in the calculation of the load carried. Tare weight is also employed in underwater weighing to measure body composition.

Tare weight is accounted for in kitchen scales, analytical (scientific) scales, and other weighing scales that include a button that resets the scales' display to zero when an empty container is placed on the weighing platform, allowing the scales to display only the weight of the container's contents.

Net weight (weight of the goods) = gross weight (total weight) - tare weight (weight of the empty container).