The antecubital fossa is an important site for venepuncture and intravenous procedures. The size and location of a vein can affect the success of venepuncture and intravenous access. Several studies have investigated the superficial vein morphometry, but they had small sample sizes or focused on specific populations or groups. Therefore, we conducted a prospective study with large participants in general population to analyse the morphology of the antecubital superficial vein and identify the association of sex, age and body mass index (BMI) with the size and location of the vein. This study collected images of superficial veins prospectively using autonomous robotic ultrasound on the antecubital area between October and November 2020. We measured the superficial vein depth, vertical diameter and horizontal diameter at the antecubital area, extracted population characteristics (sex, age and BMI), and analysed a relationship between the vein dimensions and the characteristics. In this study, data from 461 participants (201 males and 260 females) with mean age of 41.1 years were produced. The mean vein depth, mean vertical diameter and mean horizontal diameter (±standard deviation) were 4.81 (±2.17), 3.01 (±1.10) and 4.46 (±1.60) mm, respectively. We found significant differences in vein dimensions between males and females, with males having larger vertical and horizontal diameters than females (p < 0.001). The study also revealed significant differences in vein depth and dimensions among age groups and BMI subgroups (p < 0.001). These findings revealed that the superficial vein in the antecubital area was oval, with a larger horizontal diameter than vertical diameter. Morphometry revealed differences in sex, age and BMI. Understanding variations in vein dimensions among different subgroups can help medical professionals improve success rate of venous access and patient safety.