Temperature Converter
Convert between Celsius, Fahrenheit and Kelvin
How to use Temperature Converter
Convert between Celsius, Fahrenheit and Kelvin temperature scales instantly. Free online temperature converter calculator tool.
When do you need to convert temperatures?
Three temperature scales are used globally — Celsius, Fahrenheit, and Kelvin — and knowing when to use each prevents costly mistakes in cooking, science, and international communication.
- Cooking and baking: Oven temperatures are the most common conversion need. US recipes specify Fahrenheit; European ovens are labeled in Celsius. 350°F = 177°C (moderate oven). 400°F = 204°C (hot oven).
- Weather and travel: Weather reports in the US use Fahrenheit; the rest of the world uses Celsius. 30°C = 86°F (very warm summer day). 0°C = 32°F (freezing).
- Science and engineering: Kelvin is the SI unit for thermodynamic temperature. Absolute zero (0K = -273.15°C) is the foundation of thermodynamics. Chemical reactions, material properties, and radiation calculations use Kelvin.
- Medical: Body temperature: 37°C = 98.6°F. Fever threshold: 38°C = 100.4°F. Medical equipment in the US uses Fahrenheit; international medical literature uses Celsius.
- Industrial processes: Melting points, reaction temperatures, and material specifications in international supply chains require conversion between systems.
Key reference points: Absolute zero: 0K = -273.15°C = -459.67°F. Water freezes: 0°C = 32°F = 273.15K. Body temperature: 37°C = 98.6°F = 310.15K. Water boils: 100°C = 212°F = 373.15K.
Frequently Asked Questions
What is the formula to convert Celsius to Fahrenheit?
F = (C × 9/5) + 32. Or equivalently: F = (C × 1.8) + 32. To reverse: C = (F - 32) × 5/9. Mental shortcut: double the Celsius temperature and add 30 for an approximation (accurate to ±2°F in the 0-100°C range).
What is absolute zero and why does it matter?
Absolute zero (0 Kelvin = -273.15°C) is the theoretical minimum temperature — the point at which all molecular motion ceases. It is physically impossible to reach (only approach asymptotically). It defines the Kelvin scale and is fundamental to thermodynamics, quantum mechanics, and superconductor research.
Why does Fahrenheit exist when Celsius is more logical?
Daniel Fahrenheit created his scale in 1724, setting 0°F as the lowest temperature he could achieve with a brine solution, and 96°F as body temperature (later adjusted to 98.6°F). Anders Celsius created his scale in 1742 using water's freezing and boiling points — more scientifically intuitive. Both were improvements over earlier arbitrary scales.
What is the difference between Celsius and Centigrade?
They are the same scale — 'Centigrade' (Latin for 100 steps) was the original name, referring to the 100-degree interval between water's freezing and boiling points. It was officially renamed Celsius in 1948 in honor of Anders Celsius. Both terms refer to exactly the same temperature scale.
At what temperature are Celsius and Fahrenheit equal?
At exactly -40°. At -40°C = -40°F, both scales read the same value. This is because the two scales have different zero points and different step sizes — they cross at -40°.
Celsius vs Fahrenheit vs Kelvin vs Rankine
Celsius is the metric standard — anchored to water's phase transitions. Fahrenheit offers finer granularity for typical human-experienced temperatures (0-100°F covers most of human habitation). Kelvin is the absolute thermodynamic scale — no negative values, essential for physics. Rankine is Fahrenheit's absolute scale counterpart (0°R = absolute zero) — used in some US engineering applications. For everyday use: Celsius or Fahrenheit depending on your country. For science: always Kelvin.