What this converter does
This tool converts a temperature between the Fahrenheit and Celsius scales in either direction. Choose "°F to °C" to turn a Fahrenheit reading into Celsius, or "°C to °F" for the reverse. It is a pure unit-conversion tool, so the result is the same anywhere in the world. Both scales accept negative values, since temperatures can fall below the zero of either scale.
How to use it
Pick the conversion direction, type the temperature into the field that appears, and read the converted value plus the worked formula below it. Decimal inputs such as 98.6 are fine, and the answer is rounded to two decimal places.
The formula explained
The Celsius and Fahrenheit scales are linked by an affine (straight-line) relationship. Fahrenheit puts the freezing point of water at 32 and the boiling point at 212, a span of 180 degrees, while Celsius spans 100 degrees over the same range. The ratio \(180/100 = 1.8\) (the same as \(9/5\)) is the slope between them.
To go from Fahrenheit to Celsius: $$^{\circ}\text{C} = (^{\circ}\text{F} - 32) \div 1.8$$ To go from Celsius to Fahrenheit: $$^{\circ}\text{F} = (^{\circ}\text{C} \times 1.8) + 32$$ Note that \(1.8 = 9/5\) exactly, and dividing by 1.8 is the same as multiplying by \(5/9\) (about 0.5556).
Worked example
Convert 75 °F to Celsius: subtract 32 to get 43, then divide by 1.8 to get 23.888..., which rounds to 23.89 °C. The full calculation is $$^{\circ}\text{C} = (75 - 32) \div 1.8 = 43 \div 1.8 = 23.888\ldots \approx 23.89$$ Going the other way, 25 °C becomes $$^{\circ}\text{F} = (25 \times 1.8) + 32 = 45 + 32 = 77$$ which is 77 °F.
FAQ
At what temperature do the two scales meet? At −40 degrees: −40 °F equals exactly −40 °C, the only point where both scales read the same number.
What is normal body temperature? About 98.6 °F, which is 37 °C.
Can I enter values below absolute zero? The calculator does not block them, but anything below −459.67 °F (−273.15 °C) is physically impossible.
