Celsius to Fahrenheit Calculator

Background.

180 °C works out at exactly 356 °F, a number few oven dials show, which is why recipes printed on both sides of the Atlantic pair 180 °C with 350 °F. Six degrees hardly matters to a sponge cake. Elsewhere the decimals count: 37 °C is 98.6 °F, and a child's 38.5 °C reading is 101.3 °F.

Two operations are needed because the scales disagree about two separate things. A Celsius degree is the larger unit, worth 1.8 Fahrenheit degrees, because the span from water freezing to water boiling covers 100 degrees on one scale and 180 on the other. And the scales start counting from different places: water freezes at 0 °C but at 32 °F. So the Celsius figure is multiplied by 9/5 first and 32 is added afterwards. Do it in the other order and 180 °C turns into a scorching 381.6 °F.

The kelvin figure comes alongside for laboratory and engineering use. It has the same degree size as Celsius but counts from absolute zero, so 180 °C is 453.15 K.

What is celsius to fahrenheit calculator?

Celsius and Fahrenheit are two numbering systems for the same physical temperature. Under the SI as revised in 2019, the kelvin is fixed through the Boltzmann constant, a Celsius degree is defined as exactly one kelvin, and 0 °C is exactly 273.15 K. Fahrenheit is tied to Celsius by the exact relation °F = °C × 9/5 + 32. Water's freezing and boiling points, 32 °F and 212 °F at standard pressure, explain where the numbers came from historically, but no measured quantity enters the conversion.

How to use this calculator.

1. 01Enter the Celsius reading. Decimals and negative values are fine; the lowest accepted value is absolute zero, −273.15 °C, which is −459.67 °F.
2. 02Read the Fahrenheit result. For an oven, set the nearest temperature your dial offers; for a thermometer reading, keep the decimal.
3. 03If you are converting a change in temperature, such as a rise of 5 °C, do not use this conversion: multiply the change by 1.8 and leave out the 32.

The formula.

Two fixed points define the line. Water freezes at 0 °C and 32 °F and boils at 100 °C and 212 °F, so 100 Celsius degrees cover the same range as 180 Fahrenheit degrees. The slope is 180 ÷ 100 = 9/5, or 1.8, and the line passes through 32 °F at 0 °C, giving °F = °C × 9/5 + 32. Run backwards, °C = (°F − 32) × 5/9. Kelvin needs only an offset, K = °C + 273.15, because a kelvin and a Celsius degree are the same size. All three relations are exact by definition, so the results carry no rounding beyond what you choose when you read them.

A worked example.

Frequently asked questions.

References& sources.

1. [1]National Institute of Standards and Technology (2008). NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), Appendix B: Conversion Factors.
2. [2]Bureau International des Poids et Mesures (2019). The International System of Units (SI), 9th edition — defines the kelvin via the fixed Boltzmann constant and the exact offset between the Kelvin and Celsius scales.