The conversion

125°F = 51.67°C

°C = (°F − 32) × 5/9, so (125 − 32) × 5/9 = 51.67.

As an outdoor air temperature, 125 °F sits in the hot 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 125 °F.
FahrenheitCelsius
120 °F48.89 °C
121 °F49.44 °C
122 °F50 °C
123 °F50.56 °C
124 °F51.11 °C
125 °F51.67 °C
126 °F52.22 °C
127 °F52.78 °C
128 °F53.33 °C
129 °F53.89 °C
130 °F54.44 °C

The other direction

51.67 °C converts back to 125 °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.