Temperature Converter

All values assume standard atmospheric pressure (1 atm). Water's freezing and boiling points shift at different pressures and altitudes.

Celsius (°C)

The Celsius scale, defined by Anders Celsius in 1742, sets 0° at the freezing point of water and 100° at its boiling point at sea level. Its 100-degree span makes it intuitive for everyday weather, cooking, and science, and it is the standard scale in most of the world.

Fahrenheit (°F)

Proposed by Daniel Gabriel Fahrenheit in 1724, this scale places water's freezing point at 32° and its boiling point at 212° — a 180-degree span. Its finer degree increments are well suited to describing air temperature and body temperature, and it remains the everyday scale in the United States and a few other territories.

Kelvin (K)

Kelvin is the SI base unit of temperature and an absolute scale: it begins at absolute zero (0 K), the point at which molecular motion theoretically stops. A one-kelvin change equals a one-degree-Celsius change, so the two scales differ only by their zero point (273.15). Because Kelvin has no negative values, it is used throughout physics, chemistry, and engineering. Note that Kelvin values are written without the degree symbol — "298 K", not "298°K".

The Two Things That Change

Every temperature conversion adjusts for two differences between scales: the size of one degree and the position of zero. Celsius and Fahrenheit differ in both (a Fahrenheit degree is 5/9 the size of a Celsius degree, and their zeros are offset by 32°). Celsius and Kelvin share the same degree size, so only the zero point (273.15) differs.

Step by Step: Celsius to Fahrenheit

1. Scale the degree size — multiply the Celsius value by 9/5 (1.8).
2. Shift the zero point — add 32.
3. Example: 30°C → 30 × 1.8 = 54 → 54 + 32 = 86°F.

Step by Step: Fahrenheit to Celsius

1. Reverse the zero shift — subtract 32.
2. Reverse the degree scaling — multiply by 5/9.
3. Example: 86°F → 86 − 32 = 54 → 54 × 5/9 = 30°C.

Because the operations are reversible, converting back and forth always returns the original value. This calculator applies these formulas instantly across all three scales as you type.

Temperature conversion is a daily necessity whenever people, recipes, or instruments span different measurement systems:

Travel & Weather
A forecast of 30°C means little to someone used to Fahrenheit (it's a warm 86°F). Converting helps travelers pack appropriately and understand local conditions.

Cooking & Baking
Recipes from different countries list oven temperatures in Celsius or Fahrenheit. Converting accurately (e.g., 180°C = 356°F) is the difference between a perfectly baked dish and a burnt one.

Science & Engineering
Laboratory and industrial work uses Kelvin for gas laws, thermodynamics, and material properties, because calculations require an absolute scale with no negative values.

Health & Medicine
Body temperature and fever thresholds are quoted in both °C and °F depending on the region, so accurate conversion matters for interpreting readings correctly.

Forgetting the Order of Operations

When converting Fahrenheit to Celsius, you must subtract 32 before multiplying by 5/9. Doing it in the wrong order gives a significantly wrong answer.

Using 273 Instead of 273.15

The exact Celsius-to-Kelvin offset is 273.15, not 273. Rounding to 273 introduces a 0.15-degree error that matters in scientific work.

Confusing the 9/5 and 5/9 Factors

Multiply by 9/5 (1.8) when going to Fahrenheit; multiply by 5/9 when going to Celsius. Swapping them is the most common conversion error.

Writing "°K"

Kelvin is never written with a degree symbol. The correct form is "300 K", not "300°K".