The standard weight used for the calibration of scales and based on the OIML (International Organization of Legal Metrology) classification depends on the accuracy class of the scale being calibrated.

For example, if the scale being calibrated is a class M2 scale, then the standard weight used will be a class M2 weight. Similarly, if the scale being calibrated is a class F1 scale, then the standard weight used will be a class F1 weight. OIML has established six accuracy classes for standard weights, ranging from E1 (highest accuracy) to M3 (lowest accuracy). The higher the accuracy class of the weight, the more precise the scale calibration will be.

In general, the standard weights used for calibration purposes are made of highly polished stainless steel or brass and are available in a range of sizes from very small weights (e.g., 1 mg) to very large weights (e.g., 100 kg or more). These weights are usually traceable to national or international standards and are calibrated at regular intervals to ensure their accuracy.