A UV exposure dosimetry system includes at least one UV sensor that accurately measures the UV irradiance intensity. The UV dosimetry system integrates the measured UV irradiance intensity over time to calculate the real-time UV dosage and the vitamin D production by taking into account factors comprising UV sensor location, body surface area, clothing coverage, and sunscreen usage. Based on the measurement, the system can predict the time remaining to skin burn and the time remaining to reach daily goal of vitamin D production. The system also calculates the UV index in real-time, and can crowd source the measured data in a network. The UV dosimetry system supports multi-user control through an advanced and user friendly input and output interface.