Using the Nest app: Tap on the Thermostat circle > Tap on the Settings cog in the top right corner of the screen > Scroll down to Safety Temperature in the Options section > Temperature units > Choose Fahrenheit or Celsius. The unit highlighted in the white box is the unit you have selected.
On the Nest Thermostat: Push the Thermostat > Turn the dial clockwise to the Settings cog > Press the Thermostat in to select > Turn the dial clockwise through the blue circles until you find the temperature unit > Push the Thermostat to select the unit.
