Abstract This paper presents a rigorous experimental study to establish an accurate and reliable correlation equation for converting Reid Vapor Pressure (RVP) measurements to True Vapor Pressure (TVP) for live crude oils. While RVP is a widely used and standardized measure of volatility, it provides only an empirical snapshot and is often insufficient for modern crude oil streams that contain significant light hydrocarbon components. TVP, by contrast, offers a thermodynamically accurate measure of a crude's volatility under specific operational conditions, which is critical for ensuring tank farm safety, managing evaporative emissions, and complying with stringent environmental regulations. The study was conducted on-site at three major oil and gas processing plants using a portable TVP analyzer to capture live data. The results demonstrate that the widely recognized API MPMS correlation consistently and significantly underestimates the true vapor pressure of these crude oils, confirming its unsuitability for "live" streams. Based on this live dataset, a new, site-specific correlation equation was developed and validated. The new equation, which utilizes a dynamic, empirically determined constant, was shown to provide a high degree of accuracy with minimal percentage error when compared to the direct TVP measurements. This research bridges a critical gap in current industry practice by providing a standardized, validated method to accurately derive TVP from RVP data, thereby enhancing safety, improving emissions control, and ensuring regulatory compliance.