Fahrenheit to Celsius Converter

How to use this Fahrenheit to Celsius calculator

What this calculator does. This tool converts one temperature between the Fahrenheit and Celsius scales and also shows the Kelvin equivalent for context. It is useful when a weather report, recipe, appliance setting, laboratory note, or technical document uses a temperature scale different from the one you normally read. The conversion is an exact mathematical identity between scales; it does not predict weather, assess fever severity, or determine whether a material is safe at a given temperature.

When to use it. Use it to translate a U.S. weather forecast into Celsius, convert an oven temperature before cooking, check an engineering or science specification, or compare a temperature with familiar reference points such as water freezing and boiling. The NIST overview of temperature units explains the role of kelvin and degree Celsius in the International System of Units.

How to calculate. The calculator opens with a complete demonstration: 98.6 °F, which equals 37 °C and 310.15 K. The example workbook is ready immediately. To make your own conversion:

1. Replace the value in Temperature in Fahrenheit, or edit Temperature in Celsius instead. The other field updates from whichever field you changed most recently.
2. Read Primary conversion for the equality, then review the Fahrenheit, Celsius, freezing-offset, and Kelvin cards.
3. Use the reference table to compare the current value with standard temperature landmarks.
4. Select Download Excel to export the current typed inputs and calculated outputs. Select Reset to clear both temperature fields and all calculated content. After Reset, Excel export is disabled until a complete valid temperature is entered again.

Input guide. Temperature in Fahrenheit is a required finite decimal measured in degrees Fahrenheit. Enter plain numbers such as 72.5 or -40; a period is the decimal separator, and scientific notation such as 1e3 is rejected. Increasing Fahrenheit raises Celsius by 5/9 of a degree for each 1 °F increase. A common mistake is treating a temperature conversion like a simple ratio: 64 °F is not twice 32 °F because the scales have different zero points. Temperature in Celsius follows the same format rules and is also a required finite decimal when it is the active field. A realistic entry is 20 °C. Increasing Celsius by 1 °C raises Fahrenheit by 1.8 °F.

Output guide. Primary conversion states the exact relationship using rounded display values. Fahrenheit and Celsius repeat the canonical values in their respective units. Difference from water freezing is the Celsius temperature minus 0 °C; a negative number is below the conventional freezing point of pure water at standard pressure, zero is the reference point, and a positive number is above it. Kelvin equivalent adds 273.15 to Celsius. Kelvin cannot be negative in physical temperature measurement; this calculator therefore rejects values below absolute zero. The pills at the top mirror the current Fahrenheit and Celsius results. The reference table lists the current input plus water freezing, water boiling, and the special point where the Fahrenheit and Celsius numbers are both -40.

Worked example. Starting from 98.6 °F, subtract 32 to obtain 66.6. Multiply by 5/9: 66.6 × 5/9 = 37. Therefore, 98.6 °F = 37 °C. Adding 273.15 gives 310.15 K. These are the same values shown on first open and written to the startup Excel workbook.