Diagnosis
You have maintained data for a variable-size item. Your entry resultsin a quantity calculation.
All quantity calculations in BOMs are executed in the SI unit. For thisreason, all quantities must be converted to SI units.
Depending on the entry, conversions between different units ofmeasurement are necessary, either within a dimension or betweendifferent dimensions. In this case, conversion can only be carried outvia the conversion factors recorded in the material master.
If the corresponding size units are not supported or the conversionfactors are not maintained in the material master, no conversion ispossible.
Example 1:
Size 1 100
Size 2 2
Size unit SQCM
Var-size part unit SQM
As the units of measure QCM and QM have the same dimension (area), QCMcan be converted to QM.
Example 2:
Size 1 100
Size 2 2
Size unit CM
Var-size part unit PC
The units of measure have different dimensions.
(QCM --> area; ST --> no dimension).
In this case, conversion is only possible if conversion factors arestored in the material master.

Procedure
Check your entries.