TemperatureConverter
Instantly convert temperature units including Celsius, Fahrenheit, and more.
About Temperature Units
Temperature is a measure of the average kinetic energy of particles in a substance — loosely speaking, how 'hot' or 'cold' something is. Three scales are in widespread use: Celsius (°C) defines 0° as the freezing point of water and 100° as its boiling point at standard atmospheric pressure; Fahrenheit (°F), used primarily in the United States, sets those points at 32° and 212°; Kelvin (K) is the SI thermodynamic scale starting at absolute zero, the theoretical minimum where molecular motion would cease. Unlike length or mass, converting between temperature scales requires more than simple multiplication — different zero points mean you must shift as well as scale.
Each scale has a distinct origin. Daniel Gabriel Fahrenheit (1724) anchored his scale on three reproducible reference points: the freezing point of brine (0 °F), the freezing point of pure water (32 °F), and approximate human body temperature (96 °F, later adjusted to 98.6 °F). Anders Celsius (1742) first proposed a reversed scale with 0° at boiling and 100° at freezing; colleagues inverted it after his death to give the intuitive form we use today. William Thomson (Lord Kelvin) defined the absolute thermodynamic scale in 1848, starting at −273.15 °C (the extrapolated zero of the ideal-gas law), making negative temperatures physically impossible.
Temperature conversion appears in everyday life across cooking, weather forecasting, medicine, manufacturing, and science. A recipe developed in the US at 350 °F needs to be set at 177 °C in a European oven. A patient's fever of 39 °C translates to 102.2 °F for a US caregiver. Industrial processes specify operating temperatures in Kelvin when thermodynamic efficiency must be calculated precisely. Understanding all three scales — and the formulas connecting them — is essential for anyone working across borders or between scientific and everyday contexts.
Common Temperature Conversions
| From | To |
|---|---|
| 0 °C (freezing) | 32 °F — 273.15 K |
| 20 °C (room temp) | 68 °F — 293.15 K |
| 37 °C (body temp) | 98.6 °F — 310.15 K |
| 100 °C (boiling) | 212 °F — 373.15 K |
| −40 °C | −40 °F — 233.15 K |
| −273.15 °C (abs. zero) | −459.67 °F — 0 K |
| 180 °C (baking) | 356 °F — 453.15 K |
| −18 °C (freezer) | 0 °F — 255.15 K |
| 5 °C (refrigerator) | 41 °F — 278.15 K |
| 350 °F (oven) | 176.7 °C — 449.8 K |
| 1,000 °C (furnace) | 1,832 °F — 1,273.15 K |
| −196 °C (liquid N₂) | −320.8 °F — 77.15 K |
| 5,778 K (Sun surface) | 5,504.85 °C — 9,940.7 °F |
| 98.6 °F (body temp) | 37 °C — 310.15 K |
| 72 °F (comfortable) | 22.2 °C — 295.35 K |
Frequently Asked Questions
°F = (°C × 9/5) + 32. For example, 25 °C × 1.8 + 32 = 77 °F. To reverse it: °C = (°F − 32) × 5/9.
At −40°, both scales coincide: −40 °C = −40 °F. This is the only point where the two scales give the same numerical reading.
Absolute zero is 0 K = −273.15 °C = −459.67 °F. It is the coldest theoretically possible temperature, where all classical molecular motion would stop. It cannot be fully reached in practice but has been approached within billionths of a Kelvin in laboratory experiments.
The classic value is 37 °C (98.6 °F), but healthy body temperature ranges from about 36.1 to 37.2 °C depending on the measurement site, time of day, and individual.
'Centigrade' was the older name for the Celsius scale, formally renamed to 'Celsius' in 1948 by the International Committee of Weights and Measures. The two are identical — 0° is freezing water, 100° is boiling water — so the terms are interchangeable in everyday use.
Most people find 18–22 °C (64–72 °F) comfortable for resting. Activity level, humidity, and clothing affect perceived comfort. The WHO recommends at least 18 °C (64 °F) indoors for healthy adults and at least 21 °C (70 °F) in rooms with elderly people or young children.
The Kelvin scale starts at absolute zero, eliminating negative values and making thermodynamic calculations such as the ideal gas law (PV = nRT) directly proportional. In equations involving temperature ratios (efficiency of heat engines, for example), Celsius would give nonsensical negative results; Kelvin gives physically meaningful ones.
A useful approximation: subtract 30, then halve. For example, 70 °F → (70 − 30) / 2 = 20 °C (exact answer is 21.1 °C). For more precision, subtract 32 and multiply by 5/9.