浊度测量是对液体（通常是水）透明度的相对测量。它是水的一种光学特性，由光源照射时的散射光量来定义。散射光越多，浊度越大。许多颗粒都会造成浊度，包括粘土、淤泥、小的无机物和有机物、藻类、溶解的有色有机化合物和其他微小生物。浊度通常用奈菲尔浊度单位（NTU）来测量，但在某些应用领域和国家也可能使用 FTU（甲臢浊度单位）和 FAU（甲臢衰减单位）。

In drinking water treatment, the raw water turbidity is measured as well as the organics (and other physical parameters) to define the general water quality entering the works which may drive the coagulation control. Downstream of clarification, turbidity is monitored to ensure that it is being removed at each stage as during disinfection, turbidity must be low (typically <1NTU) to ensure effective disinfection of the final water. A final water turbidity measurement is often between 0.02 and 0.1NTU.

在自然水源中，测量浊度可用于评估水道中的自然变化水平，或用于评估任何排放物对水道的影响。

作为一种相对测量，它的测量方法相对明确，可以最大限度地减少不同仪器设计之间的差异。ISO7027 或 EPA 180.1 等标准对此都有规定。