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The maximum weighing capacity, conventionally $\mathrm{Max}$, specifies the upper capacity of a weighing scale; the OIML definition excludes additional capacity provided by an additive tare device.^[ref] A display reset does not by itself establish a new physical load capacity.

For a chosen model with a subtractive tare device, let $\mathrm{Max}=5\mathrm{kg}$ and suppose the combined gross mass on the load receptor must satisfyA container with tare mass $1.2\mathrm{kg}$ leaves at most $3.8\mathrm{kg}$ for net mass. Pressing the tare device can make the display read zero with that container present, but the container remains part of the supported mass. This calculation assumes the stated subtractive-tare model; it does not assign the same capacity budget to a scale with an additive tare device.

The maximum safe load describes a different boundary: the static load an instrument can carry without permanently changing its metrological qualities. It does not define the upper end of its specified weighing capacity.^[ref] For example, an instrument could have a declared $\mathrm{Max}$ of $5\mathrm{kg}$ and a separately declared maximum safe load of $7\mathrm{kg}$. Those hypothetical markings would not turn a $6\mathrm{kg}$ indication into a measurement within the declared $5\mathrm{kg}$ weighing capacity.

A subtractive tare device is a tare device whose operation reduces the weighing range available for net loads.^[ref] Its zero display accounts for a load already present, while that load continues to occupy part of the instrument's capacity.

Consider a chosen model with maximum weighing capacity $\mathrm{Max}=10\mathrm{kg}$ and no additive tare capacity. If a container of tare mass $T$ is supported on the load receptor, the admissible net mass $N$ in this model satisfiesWith $T=2.5\mathrm{kg}$, the largest net load in this capacity budget is $7.5\mathrm{kg}$. Adding $8\mathrm{kg}$ after taring would produce gross mass $10.5\mathrm{kg}$, even though the desired net indication is below $10\mathrm{kg}$.

Changing to a $0.8\mathrm{kg}$ container would leave $9.2\mathrm{kg}$ available for net mass in the same model. This is a physical consequence of reducing the supported tare mass, rather than a benefit obtainable by repeatedly resetting the display.

An additive tare device is defined by retaining the net-load weighing range. Therefore the equation above is a model for subtractive tare and a shared gross-load bound, rather than a universal rule that every scale's printed $\mathrm{Max}$ includes every possible tare allowance. The chosen container, allowed tare range and instrument capacity must describe the same load configuration.

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.