The traditionally quoted normal human body temperature is 98.6 °F. That figure corresponds to 37 °C and represents a population average rather than an exact target that every healthy person should match. A person’s normal temperature can shift with age, activity, hormones, illness, time of day, and the site and method of measurement.
The 37 °C benchmark became widely known through the work of German physician Carl Reinhold August Wunderlich, whose 1868 temperature studies helped establish clinical thermometry. The Fahrenheit conversion is 98.6 °F, although the historical figure was often presented too precisely and without emphasizing normal variation.
Oral, rectal, ear, armpit, and skin measurements do not produce identical readings. Body temperature also tends to be lower in the morning and higher later in the day. A common mix-up is treating 100.4 °F as normal; that value is widely used as a fever threshold, especially for an oral temperature, though clinical interpretation depends on context. Thus 98.6 °F is the canonical quiz answer, not a universal constant.