You can take a temperature using the mouth (oral), anus (rectal), armpit (axillary), or ear (tympanic). But the temperature readings vary depending on which one you use, and you need an accurate body temperature to determine if a fever is present. Medical research hasn't determined an exact correlation between oral, rectal, ear, armpit, and forehead temperature measurements. When you talk with your doctor about your temperature, be sure to say what method was used to take the temperature. Generally, the correlation of temperature results are as follows: The average normal oral temperature is 37°C. A rectal temperature is 0.3°C to 0.6°C higher than an oral temperature. An ear (tympanic) temperature is 0.3°C to 0.6°C higher than an oral temperature. An armpit (axillary) temperature is usually 0.3°C to 0.6°C lower than an oral temperature. A forehead (temporal) scanner is usually 0.3°C to 0.6°C lower than an oral temperature. Source: www.webmd.com