Ear, oral, and rectal temperatures are considered the most accurate readings of actual body temperature. Underarm (axillary) and forehead temperatures are considered to be the least accurate because they’re taken outside of the body rather than inside.Click to see full answer. In this way, do you need to add a degree when taking temperature under the arm?An underarm temperature is slightly lower and a rectal temperature is slightly higher. When reporting a temperature to your doctor state the method and actual temperature and don’t add or subtract a degree for the method. A digital thermometer is not expensive and provides accurate readings. how accurate is underarm temperature? An armpit (axillary) temperature is usually 0.3°C (0.5°F) to 0.6°C (1°F) lower than an oral temperature. A forehead (temporal) scanner is usually 0.3°C (0.5°F) to 0.6°C (1°F) lower than an oral temperature. Simply so, how many degrees do you add when you take a temperature under the arm? 3 C to . 6 C) degrees below rectal, ear, and temporal readings. Add . 5 to 1.0 when taking orally or under the arm to determine the comparable rectal temperature.Do you add 1 degree under the armpit?An ear (tympanic) temperature is 0.5°F (0.3°C) to 1°F (0.6°C) higher than an oral temperature. An armpit (axillary) temperature is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature.