Unit inconsistency in forensic blood and breath alcohol reporting

An inconsistency exists between statutory definitions of blood alcohol concentration as a percent by weight, a mass/mass concentration, and modern forensic laboratory reporting based on mass/volume concentration. Percent by weight (mass/mass) and grams per deciliter (mass/volume) are not equivalent units for whole blood because blood has a density of approximately 1.055-1.06 g/mL at 37 °C. When g/dL values are treated as equivalent to percent by weight, BAC is overreported by approximately 5.5-6%. The same inconsistency affects breath alcohol values when units are not properly reconciled.