Celsius to Fahrenheit Converter

How to use the Celsius to Fahrenheit calculator

What this calculator does. This tool converts one temperature value between the Celsius and Fahrenheit scales and also reports the equivalent kelvin value. It is useful for reading weather forecasts, following recipes, checking appliance settings, interpreting laboratory notes, and comparing technical specifications that use different temperature scales. It performs an exact scale conversion; it does not estimate heat index, wind chill, oven accuracy, measurement uncertainty, or how a temperature will feel to a person.

When to use it. Use it when a forecast is given in Celsius but your preferred scale is Fahrenheit, when an international recipe lists an oven setting in Celsius, when a product manual uses Fahrenheit, or when you need a quick cross-check for classroom or engineering work. The conversion relationship is standardized; the NIST guide to temperature units explains how Celsius, Fahrenheit, and kelvin intervals relate.

How to calculate. The calculator opens with a ready-to-use demonstration: 20 °C equals 68 °F, and the example Excel workbook is immediately available. To replace the example:

1. Type a value in Temperature in Celsius to calculate Fahrenheit, or type in Temperature in Fahrenheit to calculate Celsius. Your most recently edited field becomes the source.
2. Read Converted temperature for the opposite scale. The supporting cards show Celsius, Fahrenheit, Kelvin equivalent, and Difference from freezing.
3. Use the Temperature reference table to compare the current value with absolute zero and the freezing and boiling points of water.
4. Select Download Excel to export the current validated inputs and outputs. Select Reset to clear the demonstration and all calculated data; Excel export remains unavailable until a complete valid value is entered again.

Input guide. Temperature in Celsius is an optional decimal field measured in degrees Celsius. Enter a plain number with a period as the decimal separator, such as 20, -5.5, or 100. Values below -273.15 °C are rejected because they fall below absolute zero. Increasing the Celsius value always increases the Fahrenheit result by 1.8 °F for every 1 °C. A common mistake is typing the degree symbol or a comma decimal; this calculator intentionally accepts only an unambiguous plain numeric form. Temperature in Fahrenheit follows the same input rules but uses degrees Fahrenheit. A realistic example is 68. Values below -459.67 °F are rejected. Increasing Fahrenheit by 1 °F raises Celsius by 5/9 °C. Do not fill both fields independently and expect two separate calculations: editing either field updates the other so the pair always represents one temperature.

Output guide. Converted temperature is the primary opposite-scale result and is an exact identity rounded only for display. Celsius and Fahrenheit show the same physical temperature on their respective scales. Kelvin equivalent is the absolute-temperature representation; it cannot be negative for a physically valid input. Difference from freezing shows the signed distance from 0 °C: zero is water's commonly used freezing reference point, a negative value is below it, and a positive value is above it. The summary pills repeat the three scale values for quick scanning. In the table, Reference point names each landmark, while the Celsius, Fahrenheit, and Kelvin columns show equivalent values.

Worked example. The startup value is 20 °C. Multiply 20 by 9/5 to get 36, then add 32. The result is exactly 68 °F. Adding 273.15 gives 293.15 K, and the value is 20 °C above the freezing reference. Reversing the conversion gives (68 – 32) × 5/9 = 20 °C, confirming that both inputs describe the same temperature.

Learn more. For a government reference that lists the conversion equations directly, see the National Weather Service temperature conversion resource.