Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and more.
Temperature is one of the most frequently converted quantities in daily life. Whether you are following a recipe from a foreign cookbook, checking a weather forecast abroad, or calibrating laboratory equipment, knowing how Celsius, Fahrenheit, and Kelvin relate to each other is a practical skill. Each scale was designed with different reference points, and each is still actively used in different parts of the world.
Popular Temperature Conversions
Standards Note: Temperature Uses a Formula, Not Just a Factor
NIST treats Celsius-Fahrenheit conversion as an exact formula instead of a simple multiply-only factor because the two scales use different zero points as well as different step sizes.
The Three Major Temperature Scales
Fahrenheit was developed by Daniel Gabriel Fahrenheit in 1724, with water freezing at 32°F and boiling at 212°F — a 180-degree span. It remains the primary scale in the United States for weather, cooking, and body temperature. Celsius (formerly Centigrade) was defined by Anders Celsius in 1742 with water freezing at 0°C and boiling at 100°C — a more intuitive 100-degree span. It is the standard everywhere outside the US and is used in all scientific contexts. Kelvin, the SI base unit for thermodynamic temperature, starts at absolute zero (−273.15°C), the theoretical point at which all molecular motion stops. A temperature difference of 1 Kelvin equals 1°C.
Conversion Formulas
The Fahrenheit-to-Celsius formula is: °C = (°F − 32) × 5/9. Going the other way: °F = (°C × 9/5) + 32. For Kelvin: K = °C + 273.15. A useful memory trick: 0°C = 32°F, 100°C = 212°F, and body temperature is 37°C = 98.6°F. For rough mental math, double the Celsius temperature and add 30 to get an approximate Fahrenheit reading (e.g., 20°C → 40 + 30 = 70°F; actual is 68°F — close enough for everyday purposes).
| Reference Point | Value |
|---|---|
| Absolute zero | −273.15°C / −459.67°F / 0 K |
| Water freezes | 0°C / 32°F / 273.15 K |
| Room temperature | 20–22°C / 68–72°F |
| Body temperature | 37°C / 98.6°F |
| Water boils | 100°C / 212°F / 373.15 K |
| Oven (moderate) | 180°C / 356°F |
Why Two Systems Still Coexist
The United States is the only major country that still uses Fahrenheit for everyday weather and cooking. The scale provides finer resolution within the typical human comfort range (roughly 0°F–100°F corresponds to extremely cold to extremely hot weather), which some argue makes it more intuitive for non-scientific use. Celsius is more logical for scientific work because it ties directly to water's phase transitions, which are fundamental reference points in chemistry and biology. In practice, most thermometers now display both scales.
Comparing Celsius and Fahrenheit temperature scales | Pre-Algebra | Khan Academy
Khan Academy explains why Celsius and Fahrenheit feel different, how their reference points line up, and what that means for common temperature conversions.
Video source: Khan Academy
Further Reading
Sources & References
- NIST — Temperature Conversions — Kelvin, Celsius, and Fahrenheit conversion formulas from NIST.
- BIPM — The International System of Units (SI) — SI definitions for thermodynamic temperature.