The product of concentrations of calcium and phosphate (in mg / dL) is estimated to be < 60 mg 2 / dL 2 (< 4.8 mmol 2 / L 2) normally; when the product exceeds 70 mg 2 / dL 2 (5.6 mmol 2 / L 2), precipitation of calcium phosphate crystals in soft tissue is much more likely.