Background: Patient factors, such as sex and body mass index (BMI), are known to influence patient radiation exposure. Body surface area (BSA) and its association with patient radiation exposure has not been well studied. Methods and Results: We analysed height, weight, BMI and BSA in consecutive patients undergoing cardiac catheterisation and percutaneous coronary intervention (PCI) at a high-volume Australian centre between September 2016 and April 2020 to assess their association with dose–area product (DAP, Gycm2). The mean age of the cohort was 64.5 ± 12.3 years with males comprising 68.8% (n = 8100, 5124 diagnostic cardiac catheterisation cases and 2976 PCI cases). Median male BMI was 28.4 kg/m2 [IQR 25.2–32.1] versus 28.8 kg/m2 [24.7–33.7] for females, p = 0.01. Males had higher BSA (2.0 ± 0.2 m2) than females (1.78 ± 0.2 m2), p = 0.001. Each 0.4 m2 increase in BSA conferred a 1.32x fold change in DAP (95% CI 1.29–1.36, p ≤ 0.001). Each 5 kg/m2 increase in BMI was linked to a 1.13x DAP fold change (1.12–1.14, p ≤ 0.001). Male sex conferred a 1.23x DAP fold change (1.20–1.26, p ≤ 0.001). Multivariable modelling with BMI or BSA explained 14% of DAP variance (R2 0.67 vs. 0.53 for both, p ≤ 0.001). Conclusions: BSA is an important anthropometric measure between the sexes and a key predictor of radiation dose and radiation exposure beyond sex, BMI, and weight.