Abstract Aims Coronary artery calcification (CAC) measured on cardiac computed tomography (CT) is an important risk marker for cardiovascular disease (CVD) and has been included in the prevention guidelines. The aim of this study was to describe CAC score reference values in the middle-aged and elderly population and to develop a freely available CAC calculator. Methods and results All participants from two population-based cardiac CT screening cohorts (DanRisk and DANCAVAS) were included. The CAC score was measured as a part of a screening session. Positive CAC scores were log-transformed and non-parametrically regressed on age for each gender, and percentile curves were transposed according to proportions of zero CAC scores. Men had higher CAC scores than women, and the prevalence and extend of CAC increased steadily with age. An online CAC calculator was developed, http://flscripts.dk/cacscore. After entering sex, age, and CAC score, the CAC score percentile and the coronary age are depicted including a figure with the specific CAC score and 25%, 50%, 75%, and 90% percentiles. The specific CAC score can be compared to the entire background population or only those without prior CVD. Conclusion This study provides modern population-based reference values of CAC scores in men and woman and a freely accessible online CAC calculator. Physicians and patients are very familiar with blood pressure and lipids, but unfamiliar with CAC scores. Using the calculator makes it easy to see if a CAC value is low, moderate, or high, when a physician in the future communicate and discusses a CAC score with a patient.