This article introduces a universal method to quantify the triboelectric series for a wide range of polymers, establishing quantitative triboelectrification as a fundamental material property. The method involves measuring the triboelectric charge density (TECD) with respect to a liquid metal, which is soft and shape-adaptive to ensure ideal surface contact. The TECD is measured in a glove box under well-controlled conditions, with fixed temperature, pressure, and humidity. By contacting and separating with the liquid metal, the contact pressure is kept the same, and the contact intimacy is greatly enhanced to achieve reliable values. The TECD is also normalized to show the intrinsic physical property of the materials. The triboelectric series ranks various materials based on their tendency to gain or lose electrons, reflecting their natural physical properties. Static electricity occurs when there is an excess of positive or negative charges on an object's surface due to rubbing. The position of the material in the triboelectric series determines how effectively the charges will be exchanged. The triboelectric series can be used to select materials that minimize static charging to prevent electrostatic discharge or attraction. It has found renewed interest in applications such as triboelectric nanogenerators (TENGs) for energy harvesting, self-powered sensors, and flexible electronics. The study quantifies the triboelectric series by measuring the TECD of various polymers using a standardized method. The results show that the TECD is repeatable and reliable, with good long-term stability. The normalized TECD reveals the materials' capability to gain or lose electrons after contact electrification. The quantified triboelectric series provides a standard for implementing triboelectrification in applications such as energy harvesting and self-powered sensing. The study also highlights the importance of standardized measurement methods for accurate quantification of triboelectric charge density.This article introduces a universal method to quantify the triboelectric series for a wide range of polymers, establishing quantitative triboelectrification as a fundamental material property. The method involves measuring the triboelectric charge density (TECD) with respect to a liquid metal, which is soft and shape-adaptive to ensure ideal surface contact. The TECD is measured in a glove box under well-controlled conditions, with fixed temperature, pressure, and humidity. By contacting and separating with the liquid metal, the contact pressure is kept the same, and the contact intimacy is greatly enhanced to achieve reliable values. The TECD is also normalized to show the intrinsic physical property of the materials. The triboelectric series ranks various materials based on their tendency to gain or lose electrons, reflecting their natural physical properties. Static electricity occurs when there is an excess of positive or negative charges on an object's surface due to rubbing. The position of the material in the triboelectric series determines how effectively the charges will be exchanged. The triboelectric series can be used to select materials that minimize static charging to prevent electrostatic discharge or attraction. It has found renewed interest in applications such as triboelectric nanogenerators (TENGs) for energy harvesting, self-powered sensors, and flexible electronics. The study quantifies the triboelectric series by measuring the TECD of various polymers using a standardized method. The results show that the TECD is repeatable and reliable, with good long-term stability. The normalized TECD reveals the materials' capability to gain or lose electrons after contact electrification. The quantified triboelectric series provides a standard for implementing triboelectrification in applications such as energy harvesting and self-powered sensing. The study also highlights the importance of standardized measurement methods for accurate quantification of triboelectric charge density.