Temperature Converter — °C to °F to Kelvin

How Temperature Conversion Works

Temperature scales differ in two ways: the size of a single degree and the reference point for zero. Celsius (°C) sets 0 at the freezing point of water and 100 at its boiling point at sea level. Fahrenheit (°F) places those same events at 32° and 212°, making each Fahrenheit degree about 5/9 the size of a Celsius degree. Kelvin (K) uses the same degree size as Celsius but anchors zero at absolute zero. the point where all molecular motion stops, which is −273.15 °C. Rankine (°R) mirrors this absolute-zero approach but uses Fahrenheit-sized degrees, so 0 °R = −459.67 °F.

The four core formulas are:

°F = (°C × 9/5) + 32
°C = (°F − 32) × 5/9
K = °C + 273.15
°R = °F + 459.67

Common Temperature Reference Points

Knowing a handful of fixed values helps you sanity-check any conversion. Body temperature is 37 °C / 98.6 °F. Room temperature sits around 20–22 °C / 68–72 °F. Water freezes at 0 °C / 32 °F and boils at 100 °C / 212 °F (at standard atmospheric pressure). Absolute zero is 0 K / −459.67 °F / 0 °R.

A practical example: a recipe calls for a 375 °F oven. Applying the formula, (375 − 32) × 5/9 = 343 × 0.5556 ≈ 190 °C. Most metric ovens will be set to 190 °C for that same result.

When Each Scale Is Used

Celsius is the everyday standard in most countries and in all scientific work outside the United States. Fahrenheit remains common in the US for weather forecasts, cooking, and body temperature readings. Kelvin is the SI base unit for thermodynamic temperature and is used in physics, chemistry, astrophysics, and materials science. anywhere negative temperatures would be physically meaningless. Rankine appears in some engineering fields in the US, particularly thermodynamics textbooks that use Imperial units throughout.

If you work with weather APIs, note that many return values in Kelvin by default. Subtracting 273.15 converts instantly to Celsius.

Sources & Further Reading

Frequently Asked Questions

How do I convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 (or 1.8) and add 32. For example, 100°C × 1.8 + 32 = 212°F. To go the other way, subtract 32 then multiply by 5/9.

What is absolute zero in Celsius and Fahrenheit?

Absolute zero is 0 Kelvin, which equals −273.15°C or −459.67°F. It is the theoretical lowest possible temperature, where all molecular motion stops. Absolute zero has never been reached in practice, though scientists have cooled matter to within billionths of a degree of it.

When is Kelvin used instead of Celsius?

Kelvin is the SI unit for thermodynamic temperature and is used in physics, chemistry, astrophysics, and materials science — anywhere negative temperatures would be physically meaningless. Weather APIs often return temperatures in Kelvin; subtract 273.15 to convert to Celsius.

What is a normal body temperature in Fahrenheit and Celsius?

Normal adult body temperature is 37°C or 98.6°F, though individual variation is normal and typical ranges span 36.1°C–37.2°C (97°F–99°F). Fever is generally considered a temperature above 38°C (100.4°F).