The conversion

63°F = 17.22°C

°C = (°F − 32) × 5/9, so (63 − 32) × 5/9 = 17.22.

As an outdoor air temperature, 63 °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 63 °F.
FahrenheitCelsius
58 °F14.44 °C
59 °F15 °C
60 °F15.56 °C
61 °F16.11 °C
62 °F16.67 °C
63 °F17.22 °C
64 °F17.78 °C
65 °F18.33 °C
66 °F18.89 °C
67 °F19.44 °C
68 °F20 °C

The other direction

17.22 °C converts back to 63 °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.