Temperature Converter
Enter a temperature in any scale — see all three instantly.
What Is a Temperature Converter?
The world measures temperature on three scales that refuse to agree: Celsius for most countries and all of science's daily work, Fahrenheit for weather and kitchens in the United States, and Kelvin for physics. This converter translates between all three instantly — enter a temperature and select its scale, and the equivalents appear. It is the tool you reach for with a foreign recipe, an international weather forecast, an oven manual from another continent, or a lab protocol.
The scales disagree because they were anchored to different things. Fahrenheit (1714) set 0° at the coldest brine mixture its inventor could make and body temperature near 96°. Celsius (1742) anchored cleanly to water: 0° freezing, 100° boiling at sea level. Kelvin (1848) starts at absolute zero — the complete absence of thermal motion — which makes it the only scale where ratios mean anything physically.
How to Use the Temperature Converter
- Enter the temperature value.
- Select the scale it is measured in: Celsius (°C), Fahrenheit (°F), or Kelvin (K).
- Read the converted values on the other scales.
The Conversion Formulas
Celsius to Fahrenheit: °F = (°C × 9/5) + 32. Fahrenheit to Celsius: °C = (°F − 32) × 5/9. Kelvin is a simple shift: K = °C + 273.15. The famous crossover point where Celsius and Fahrenheit agree is −40 — a genuinely cold day reads identically on both scales. Useful anchors to memorize: water freezes at 0°C / 32°F, room temperature is about 21°C / 70°F, body temperature is 37°C / 98.6°F, and water boils at 100°C / 212°F.
Quick Mental Math for Travelers
- Rough Celsius-to-Fahrenheit: double the Celsius and add 30. For 20°C: 70°F — close to the exact 68°F, and good enough to choose a jacket.
- Oven temperatures: 180°C ≈ 350°F (the standard baking temperature in most of the world), 200°C ≈ 400°F, 220°C ≈ 425°F.
- Fever check: 38°C = 100.4°F is the conventional fever threshold; 39.5°C ≈ 103°F warrants prompt medical attention, especially in children.
Why doesn't Kelvin use the degree symbol?
By convention of the SI system, kelvin is an absolute unit like the meter or second, so it is written plainly: 293 K, not 293°K. The degree symbol belongs to the relative scales (Celsius and Fahrenheit), whose zeros are arbitrary reference points rather than true zeros of the quantity being measured.
What is absolute zero in Fahrenheit?
Absolute zero is 0 K = −273.15°C = −459.67°F — the temperature at which particles have minimal possible thermal motion. It cannot be reached in practice (the third law of thermodynamics), though laboratories have come within billionths of a kelvin. Any conversion result below it signals a typo in the input.
How do I convert a temperature difference rather than a temperature?
Differences convert without the offset: a change of 10°C is a change of 18°F (just multiply by 9/5), because the +32 belongs to the scale's zero point, not its step size. This matters in engineering specs ("stable within ±2°C" means ±3.6°F) and weather ("10 degrees colder tomorrow"). One kelvin of difference equals exactly one Celsius degree of difference.
Which scale do US ovens and weather use, and which do recipes elsewhere use?
US ovens, weather, and body temperatures are Fahrenheit. Most of the rest of the world — including the UK, Europe, and most international cookbooks — uses Celsius for all of it (the UK still mixes units in everyday speech). When a recipe gives a "moderate oven" without a number, that is conventionally 180°C / 350°F, roughly gas mark 4.