What is Temperature Conversion?
Convert Celsius, Fahrenheit, and Kelvin.
Supported units: Celsius (°C), Fahrenheit (°F), Kelvin (K).
Three scales, three inventors, three reference points
Temperature is unusual among physical quantities: three independent scales are still in wide use today, each designed around a different reference. Daniel Gabriel Fahrenheit (1686–1736) built the first reliable mercury thermometer in 1714 and calibrated his scale so that a brine-ice mixture was 0°F and human body temperature was around 96°F — giving 32°F for the freezing point of pure water and 212°F for its boiling point. Anders Celsius proposed his scale in 1742; curiously, his original had 0 at boiling and 100 at freezing — it was reversed after his death. Kelvin came a century later: in 1848 William Thomson (Lord Kelvin) realised there is a true physical zero — the coldest temperature possible, where molecular motion stops — and built an absolute scale starting at −273.15°C. Today Celsius is the global standard for weather and cooking; Fahrenheit survives in US domestic use (and Liberia and the Cayman Islands); Kelvin rules in science and engineering where thermodynamic calculations demand absolute values.
Where you convert temperatures every day
Weather and travel
A 30°C day sounds mild to a European and hot to an American (it's 86°F). Anyone travelling between the US and the rest of the world needs to translate weather forecasts to know what to pack.
Cooking and baking
US recipes list oven temperatures in Fahrenheit (350°F), most of the world in Celsius (175°C). Meat safety is defined in both — chicken must reach 74°C / 165°F internal — and a 10° error here is the difference between food-poisoning and a safe meal.
Medicine and health
A "normal" body temperature is 37°C / 98.6°F; fever starts around 38°C / 100.4°F. US hospitals, travel insurance, and COVID checkpoints all need both.
HVAC and climate control
Air conditioners list their capacity in BTU (US) or kilowatts (rest of world). Set-point temperatures for servers, labs, and wine cellars are specified in Celsius internationally but Fahrenheit in US manuals.
Science, materials, and industry
Thermodynamic equations require Kelvin (you cannot have "twice as hot" in Celsius — only in K). Metal melting points, semiconductor specs, and cryogenic research are almost always published in Kelvin; technicians still need to convert to the scale their instruments show.
Common Conversions
- 1 Celsius (°C) = 33.8 Fahrenheit (°F)
- 1 Celsius (°C) = 274.15 Kelvin (K)
- 1 Fahrenheit (°F) = -17.2222 Celsius (°C)
- 1 Fahrenheit (°F) = 255.928 Kelvin (K)
- 1 Kelvin (K) = -272.15 Celsius (°C)
- 1 Kelvin (K) = -457.87 Fahrenheit (°F)
FAQ
Q: How to convert Celsius to Fahrenheit?
A: F = (C × 9/5) + 32. Example: 100°C = 212°F.
Q: How to convert Fahrenheit to Celsius?
A: C = (F − 32) × 5/9. Example: 98.6°F = 37°C.
Q: What is absolute zero in Celsius?
A: Absolute zero = −273.15°C = 0 K.
Q: Why does the Celsius ↔ Fahrenheit formula use 9/5 and 32?
A: The factor 9/5 is the ratio of the scales' step sizes (Fahrenheit has 180 degrees between freezing and boiling; Celsius has 100; 180/100 = 9/5). The offset 32 is because pure water freezes at 0°C but 32°F — the zero points don't align, so you have to shift after scaling.
Q: At what temperature do Celsius and Fahrenheit read the same number?
A: −40. It's the only point where C = F, a useful trick for checking that your conversion is right.