Quality tolerance is the agreed permissible deviation of a measured parameter from its nominal or target value, making specifications workable in practice by defining the boundary between acceptable lots and those subject to rejection or price adjustment.
In trade practice
Tolerances are set for physical parameters such as moisture, broken pieces, colour score and foreign matter, as well as for chemical values such as acidity or peroxide value. Buyers and suppliers negotiate tolerances during specification alignment, often based on what processing equipment and grading lines can reliably achieve. A common mistake is specifying a target value without a tolerance, which leaves both parties unable to agree on borderline results at intake. Where a lot falls outside tolerance, the specification should also state the agreed remedy, whether rejection, regrading or a price adjustment.
In a specification
Tolerances are written into the specification as a permitted range or maximum deviation alongside each parameter, and should be consistent with the measurement uncertainty of the agreed analytical method.