Hold the button while the thermometer is off. You should see an indication that it’s reading in Fahrenheit by the “F” on the bottom. Press the button again to change the F to a C, and then the thermometer should read in Celsius.Click to see full answer. Thereof, how do I change my Walgreens thermometer from Celsius to Fahrenheit? Walgreens Thermometer :: Change Celsius to Fahrenheit Push the button to get the thermometer ON. Wait for the L with the little C on the screen. Then HOLD the button down until it changes to Fahrenheit (indicating F). Subsequently, question is, how do you change from Celsius to Fahrenheit? To convert temperatures in degrees Celsius to Fahrenheit, multiply by 1.8 (or 9/5) and add 32. Subsequently, question is, how do I change my Omron thermometer from Celsius to Fahrenheit? To change the measurement mode from °F (Fahrenheit) to °C (Centigrade), follow the procedure shown below. From the off position (blank display): 1. Press and hold the ON/OFF button for more than 5 seconds until F flashes on the display.How do I reset my digital thermometer? Method 1: Ice Water Fill a glass with ice cubes, then top off with cold water. Stir the water and let sit for 3 minutes. Stir again, then insert your thermometer into the glass, making sure not to touch the sides. The temperature should read 32°F (0°C). Record the difference and offset your thermometer as appropriate.