Allegation is a process to calculate the price of particular elements available in a mixture, which has two or more than two varieties.

Mixtures are those compounds where two different materials or more than two are mixed in order to get an end product. The word allegation helps us understand the concept of compounding ingredients, how two or more than two ingredients can be mixed in a specific ratio or proportion according to a particular design. The basic concept of allegation lies with its root words, which means determining the mean value of a specific mixture. While calculating allegation, only 1 gram of each substance is taken into consideration. It also helps in determining the strengths of individual elements or even the whole system.      

Concept of Allegation

One of the old methods which involve practical implications while solving problems of arithmetic associated with mixtures of several ingredients is an allegation. Two categories of allegations namely medial and alternate have their own significance, while allegation alternate is comparatively more complex. Allegation medial is used for determining the amount of a particular quantity within a mixture or in simple words it is used in finding the weighted mean. However, allegation alternate has a similar usage where the amount of each quantity is determined through formulas. Associated with allegation is the concept of the mixture, as allegation deals with mixtures. Mixtures are combinations of two different elements or more than two elements that also may be used to form a mixture. These elements are associated in specific proportions forming the end product. One can rely upon the concepts of ratio and proportions to determine the number of elements used in making the whole mixture.  

How to Calculate allegation? 

Answer to the question, how to calculate allegation is associated with a basic formula, 

In the whole formula, a single unit of both the elements is required whether it is a cheaper one or the dearer element, here CP is the short form of the cost price of the considered substance. Now there are a few basic rules associated with the integrated formula:

  • The difference between average price and extreme values enables one to compare between the two quantities, while in the calculation always the smaller value is subtracted from the bigger one so the end value comes out to be positive
  • The difference thus calculated needs to be placed in positions that are in the same direction as the cross lines are indicating
  • The price difference is placed on the left-hand slide while the average price occupies the right-hand side and vice versa
  • The ratio which is calculated at the end represents the level and if the price of the product gets below the level then it is visible
  • Cases having two average prices and extreme values can be easily solved through the formula of the allegation

There are a few aspects that one needs to keep in mind while calculating allegations: 

Few solvents and diluents, for example, water or white petrolatum and others have zero percentage strength

The unit of a millilitre is used for liquids like syrups

Those substances which have solid or semi-solid forms are taken in measuring units of grams

The strength which is used in the allegation formula needs to be expressed in the form of a percentage

Leading zero while proceeding with a calculation in decimals or percentages can help in reducing the chances of a wrong interpretation of the answer

29.57 mL = 1 fl. oz

28.35 gm = 1 avoirdupois oz 

Significance of Allegation 

Allegation methods are used for solving problems where parts are needed to be found out among a whole mixture. In the mixture, several elements are available in different proportions, while each varies in its strengths. It helps in understanding weighted averages, which have significance in every aspect of daily tasks. Here if the question asks one to calculate the proportion of each element within the whole mixture or the total strength of the whole system, then the allegation concept helps in doing so. Hence, the concept of allegation is important in understanding compounding ingredients in chemistry, which helps one to know how the mixing of two or more ingredients is done according to any particular design or intent. Problems that include wages, time and work or partnerships can be easily solved with the help of an allegation grid. Pharmacists often use this grid to understand what percentage of two different mixtures are needed to be mixed, each having different strengths to get the required substance at the end of the whole procedure. Textbook chapters like percentage, simple interest, profit and loss, and average have good applicability of allegation. Repeated dilutions can also be carried out with the help of allegation formulas. 


The concept of allegation deals with determining and understanding in what proportions two or more elements are being used to form a mixture. Now, a mixture is a combination of two or more substances that are available in a specific proportion. Allegation helps one to calculate the strength and proportion of each substance in the whole mixture. This concept has huge significance in chemistry, as it helps in calculating the ratio in which each substance needs to be used so that the required end product is obtained. Allegation formulas help deal with mixtures, however complex they are.