In university classrooms, chairs and tables of unique and standardized dimensions, not adaptable, are normally used. This furniture is used by all students without distinction of sex. It is usual in these cases to receive some criticisms about bad postures, in particular by female students, but no serious study has been done in this regard at this university. The purpose of this study was to determine the percentage of the male and female university population, separately, who cannot comfortably use such furniture, for which the tables and chairs of a new classroom building were taken into account. One of the reasons why a previous study has not been carried out is the difficulty of using an anthropometer to obtain the dimensions of the students, so a methodology has been used to find the necessary body dimensions for the study, from of his height only. This dimension is very easy to obtain. Additionally, the weight was included, which also included a study of student obesity, which could influence the use of the indicated furniture. The most significant result is that a percentage greater than 90% of female students have difficulty sitting and using tables in classrooms, considering the most important dimensional variables in the sitting position, so their health could be at risk, due to to the large number of hours they can spend using the chairs and tables in their classrooms. The entire student body can be included and with the results, you can determine the dimensions of the furniture, instruments, machines that will be used from now on.