物理量的量纲可以用来分析或检核几个物理量之间的关系，这方法称为量纲分析（dimensional analysis）。通常，一个物理量的量纲是由像质量、长度、时间、电荷量、温度一类的基础物理量纲结合而成。例如，速度的量纲为长度每单位时间，而计量单位为公尺每秒、英里每小时或其它单位。量纲分析所根据的重要原理是，物理定律必需跟其计量物理量的单位无关。任何有意义的方程序，其左手边与右手边的量纲必需相同。检查有否遵循这规则是做量纲分析最基本的步骤。

推导获得的方程序或计算结果是否基本上合理，惯常可以用量纲分析来检察。对于较复杂的物理状况，量纲分析也可以用来构筑合理假定（参见关联模型），然后，做严格的实验加以测试，或用已发展成功的理论仔细检试。量纲分析能够按照各种物理量的量纲，将它们详细分类。

In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their fundamental dimensions (such as length, mass, time, and electric charge) and units of measure (such as miles vs. kilometers, or pounds vs. kilograms vs. grams) and tracking these dimensions as calculations or comparisons are performed. Converting from one dimensional unit to another is often somewhat complex. Dimensional analysis, or more specifically the factor-label method, also known as the unit-factor method, is a widely used technique for such conversions using the rules of algebra.