The conversion

71°F = 21.67°C

°C = (°F − 32) × 5/9, so (71 − 32) × 5/9 = 21.67.

As an outdoor air temperature, 71 °F sits in the mild band. The other scale is on the dial beside it in the app, so a reading like this needs no conversion at all.

Convert something else

68°F

The range either side

Neighbouring values, for when the number you actually wanted was a degree or two away.

Fahrenheit to Celsius either side of 71 °F.
FahrenheitCelsius
66 °F18.89 °C
67 °F19.44 °C
68 °F20 °C
69 °F20.56 °C
70 °F21.11 °C
71 °F21.67 °C
72 °F22.22 °C
73 °F22.78 °C
74 °F23.33 °C
75 °F23.89 °C
76 °F24.44 °C

The other direction

21.67 °C converts back to 71 °F, which is the same relationship read the other way. Going from Celsius to Fahrenheit, multiply by 9/5 first and then add 32. Adding first is the usual mistake.

The full converter handles any value, in either direction, including kelvin, and shows the formula as it works.