 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 performing such conversions using the rules of algebra.dimensional analysis or the factor label method any physically meaningful equation (and any inequality and inequation) must have the same dimensions on the left and right sides. checking this is a common application of performing dimensional analysis. dimensional analysis is also routinely used as a check on the plausibility of derived equations and computations. it is generally used to categorize types of physical quantities and units based on their relationship to or dependence on other units. ==concrete numbers and fundamental units== many parameters and measurements in the physical sciences and engineering are expressed as a concrete number - a numerical quantity and a corresponding dimensional unit. often a quantity is a combination of multiple dimensions; for example, speed is a combination of length and time, e.g. 60 miles per hour or 1.4&nbsp;km per second. compound relations with "per" are expressed with division, e.g. 60&nbsp;mi/1 h. other relations can involve multiplication (often shown with Â· or implied), exponents (like m2 for square meters), or combinations thereof. sometimes the names of units obscure their compound nature. for example, an ampere is a measure of electrical current, which is fundamentally electrical charge per unit time and is measured in coulombs (a unit of electrical charge) per second, so 1a = 1c/s. one newton is kgÂ·m/s2 a unit of measure which is not compound - it cannot be decomposed into other units - is known as a fundamental unit. === percentages and derivatives === percentages are dimensionless quantities, since they are ratios of two quantities with the same dimensions. in other words, the % sign can be read 
Chemical_engineering Conversion_of_units_of_measurement Dimensional_analysis Environmental_engineering Measurement Mechanical_engineering