At the beginning of the 18th century, an important break occurred in the discipline of Western art criticism. Until that century, approaches that combined the art of painting with poetry or the artist’s biography while evaluating a work of art (especially a painting) made visual arts criticism based on literary theories. In the 18th century, firstly Roger de Piles, then Jonathan Richardson, studied on art criticism. Since emphasizing the importance of the formal qualities of an artwork in their art criticism, they separated art criticism from literary theory. Although the studies of these critics may seem to us unfounded and dubious in terms of determining the merit of a work of art, modern art criticism owes its foundations to their efforts. In this article, the scales and theories developed by these two art critics to measure the merit of an artist or a work of art have been examined. The basic principles and evaluations of their approaches, the effects of the said scales, and the reactions to the measurement tools have been examined. Roger de Piles explained his criteria for evaluating, judging a work of art in the chapter entitled Balance des Peintres in his book Cours de Peinture par Principes, published in 1708. The scale focused on the four qualities of art: composition, design, color, expression. In his scale, he determined twenty degrees. With his scale, Roger de Piles proposed to measure the merits of artists according to four basic formal qualities. Roger de Piles, gave to 57 artists a score of 0-20 for each formal quality to show how the scale worked. In this way, he tried to measure the merit of the artists of the Renaissance, Mannerist and Baroque periods. This scale also reflected Roger de Piles’ hierarchy of pictorial formal qualities. Jonathan Richardson also developed a scale similar to Roger de Piles’ scale. Richardson’s scale, on the other hand, suggested measuring composition, colouring, style, design, exploration, expression, and grace and grandeur; each with a score between 0-18. Points 18 and 17 represent the artist’s greatness, sublimity; points 16-13 represent excellence in different grades, and points 12-5 indicate mediocrity, and points between 4-1 means bad. These scales received widespread attention for the 18th century art criticism. Critics and scientists used those scales not only in the field of painting, but also in different fields such as music, mathematics, and poetry. With the rise of the romantic movement, after the first decade of the 19th century, these scales began to be viewed as insufficient, uncertain, and questionable. Thus, after the first decade of the 19th century, these scales lost their influence in the field of art criticism. This article, which aims to understand the characteristics of the scales of art criticism, was carried out based on document analysis. The main documents of this study are the books of Roger de Piles and Jonathan Richardson that published in the 18th century.