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Gross mass is the mass of the complete specified load, including its contents and the packaging counted as tare mass. For that same boundary,The gross indication in OIML's weighing terminology is obtained with neither a tare device nor a preset tare device operating, after an initial zero indication.^[ref] A full crate's gross mass consequently differs from an individual jar's gross mass, because the specified loads differ.

Consider four jars, each containing $0.50\mathrm{kg}$ of material and having an empty-container tare mass of $0.20\mathrm{kg}$. An outer crate adds $0.80\mathrm{kg}$. For the complete load, the net mass of the contents, composite tare mass, and gross mass are respectivelyThese are chosen bookkeeping values, assuming the listed components exhaust the load and each component is counted once.

Subtracting the full composite tare mass from the complete gross mass gives $3.60-1.60=2.00\mathrm{kg}$ of contents. If the jars' $0.80\mathrm{kg}$ has already been removed from an intermediate total, subtracting the same full composite tare mass again gives $1.20\mathrm{kg}$. The missing $0.80\mathrm{kg}$ is precisely the duplicated deduction. Use one load boundary and subtract each packaging component once.

The gross mass also remains relevant to maximum weighing capacity when a subtractive tare device reduces the available net-load range.^[ref] For an illustrative instrument modeled with a $1.000\mathrm{kg}$ gross-load limit, a $0.120\mathrm{kg}$ container leaves $0.880\mathrm{kg}$ for contents. At that limit the complete load still has gross mass $1.000\mathrm{kg}$, even though the tared display reports only its contents.

For a stationary ideal weighing scale, the normal contact force associated with a complete load is related to its gravitational weight. A displayed net mass is a processed indication of that load; it is not the full supported mass. Changes in the gravitational field, measurement calibration, or the load boundary must therefore be distinguished when interpreting a reading.

A preset tare value is a numerical tare mass entered or recalled for use in subsequent weighings without individually determining each container's tare. The pinned OIML terminology denotes it by $\mathrm{PT}$ and calls the measured gross or net indication minus this value a calculated net value. It can be supplied through a preset tare device rather than obtained by weighing the current empty container.^[ref]

For an original example, a stored container tare is $\mathrm{PT}=250\mathrm{g}$, but the actual empty container has tare mass $T=263\mathrm{g}$. Adding $500\mathrm{g}$ of material gives gross mass $G=763\mathrm{g}$. Applying the stored value givesalthough the actual net mass is $N=G-T=500\mathrm{g}$. Their difference isAn underestimated preset tare therefore overestimates the contents. Repeating the same discrepancy across ten containers produces a $130\mathrm{g}$ total discrepancy; more displayed digits do not remove it.

A useful physical check independently weighs representative empty containers, including the same lids and attachments used during the loaded measurement, and compares them with the stored value. Record which load components the preset represents. If it is subtracted from an indication that has already had those components removed by a tare device, the same tare mass is deducted twice. The stored number's provenance and variability belong in the measurement model and its measurement uncertainty.

A tare device establishes a zero indication on a weighing scale while a load remains on its load receptor. An additive tare device preserves the weighing range for net loads; a subtractive tare device reduces that range.^[ref]

For example, place an empty $0.40\mathrm{kg}$ container on the load receptor and operate the tare device. The display reads zero even though the scale still supports the container. Adding $1.10\mathrm{kg}$ of material gives gross mass $1.50\mathrm{kg}$ and, ideally, an indicated net mass of $1.10\mathrm{kg}$. Removing both material and container without clearing the tare would ideally give $-0.40\mathrm{kg}$. This negative indication is consistent with the changed reference.

The cancellation can be seen in a linear model. If the unrounded indication before tare is $r(m)=am+b$, and the supported container has tare mass $T$, the indicated result after adding net mass $N$ isThe additive offset $b$ and the container contribution cancel. A response scale factor $a\ne 1$ remains, so taring alone does not establish calibration across the load range.

The container's physical load remains on the scale after taring. Consequently the available maximum weighing capacity depends on the kind of tare device, even when two instruments show the same zero. A preset tare device performs a related numerical subtraction using an entered or recalled value, rather than necessarily measuring this particular empty container.

Tare mass is the specified container or packaging mass excluded when reporting net mass. It is also called tare weight in weighing terminology. The intended boundary matters: a jar alone and that jar with its lid have different tare masses. A tare device adjusts a weighing scale's indication with a load present, whereas a zero-setting device establishes zero with the load receptor unloaded.^[ref]

A simple demonstration separates the reading from the physical load. Choose an empty container of mass $m_{\mathrm{t}}=0.120\mathrm{kg}$ and an ideal weighing scale that initially reads zero. After the container is placed on the load receptor, operate the tare device. Its displayed value becomes zero while the container's mass remains $0.120\mathrm{kg}$. In a uniform gravitational field with chosen magnitude $g=9.81\mathrm{m}{\mathrm{s}}^{-2}$, its gravitational weight is stillThe supporting force remains present after the display adjustment.

In an ideal unit-gain measurement model, the tared indication for a complete load of mass $m$ is $I(m)=m-m_{\mathrm{t}}$. Adding $0.300\mathrm{kg}$ of contents gives gross mass $0.420\mathrm{kg}$ and indication $0.300\mathrm{kg}$. Removing the complete load while retaining that reference gives indication $-0.120\mathrm{kg}$. The negative indication expresses the difference from the stored reference; the removed container still has positive mass.

A preset tare device instead uses an introduced preset tare value, which can be recalled or entered without weighing each individual empty container.^[ref] For the same chosen load, using a preset of $0.100\mathrm{kg}$ gives calculated net mass $0.420-0.100=0.320\mathrm{kg}$: the contents are overestimated by 20 g. A persistently low preset produces a systematic error even with otherwise exact readings.

Composite tare mass includes several excluded components, such as all the jars and an outer crate. The gross mass example shows how to account for these components once each. The symbol $m_{\mathrm{t}}$ here denotes a mass; the terminology's use of the word weight does not change the quantity's unit from a kilogram to a unit of force.