Actually, it depends on the thermometer. Each type is broken into regular markings. The long lines are for whole number increments (1 degree, 2 degree, or 5 degree markings, generally speaking). The short lines are for in-between marks (0.5 degree, 1 degree, or even 2 degree marks). The Celsius scale is different from the Fahrenheit scale, but they are easily related to each other. If you have a Fahrenheit number, use this formula: C = 0.56 (F-32). If you have a Celsius number, use the formula: F = 1.8C + 32. Keep in mind that O C = 32F, 100 C = 212F, and body temperature 38C = 98.6F. Hope this helps.