Metabolic syndrome is a cluster of cardio-metabolic risk factors and is associated with increased mortality. There is no standard, validated way to assess the severity of aggregated metabolic syndrome risk factors. Cardiovascular and diabetes risk factor data came from two studies conducted in Australia from 2006 to 2010 in adults aged 18 or above. In medication free adults, sex-specific clinical thresholds and Principal Component Analysis were used to develop a formula to calculate a metabolic syndrome severity score (MetSSS). These scores were compared to scores derived using the same process in subgroups by sex, age, medication status, and time. We also examined the MetSSS in relation to other known risk factors. In 2125 adults (57.6±14.7years of age), the MetSSS ranged from 0 to 8.7 with a mean of 2.6. There were strong correlations (.95-.99) between the MetSSS in medication free adults and the MetSSS calculated from subgroups. MetSSS predicted medication initiation for hypertension, hyperlipidemia and hyperglycemia over six months (OR=1.31, 95% CI [1.00-1.70], per MetSSS unit, p=.043). Lower education, medication prescription, history of smoking and age were associated with higher MetSSS (all p<.05). Higher physical but not mental health quality of life was associated with lower MetSSS (p<.001). A standardized formula to measure cardio-metabolic risk factor severity was constructed and demonstrated expected relations with known risk factors. The use of the MetSSS is recommended as a measure of change within individuals in cardio-metabolic risk factors and to guide treatment and management.