Use of abbreviations and numbers varies in different fields. See a typical example from a biochemistry textbook:
The energy of a green photon . . . is 57 kilocalories per mole (kcal/mol). An alternative unit of energy is the joule (J), which is equal to 0.239 calorie; 1 kcal/mol is equal to 4.184 kJ/mol.
—LUBERT STRYER, Biochemistry
These two sentences demonstrate how useful figures and abbreviations can be; reading the same sentences would be very difficult if the numbers and units of measurement had to be written out.
Be sure to use the appropriate system of measurement for the field you are discussing and for the audience you are addressing. Scientific fields generally use metric measurements, which are the standard in most nations other than the United States.
Become familiar with the conventions governing abbreviations and numbers in your field. The following reference books provide guidelines:
MLA Handbook for Writers of Research Papers for literature and the humanities
Publication Manual of the American Psychological Association for the social sciences
Scientific Style and Format: The CSE Manual for Authors, Editors, and Publishers for the natural sciences
The Chicago Manual of Style for the humanities
AIP Style Manual for physics and the applied sciences