Temperature Converter
Convert temperature between Fahrenheit, Celsius, Kelvin, and Rankine with formula display and reference points.
Calcady™ · Calculation Report Temperature Converter calcady.com Thermal Converter22.2222 Converted Temperature22.2222 °C |
Quick Answer: Temperature Conversion Formulas
°F to °C: (°F − 32) × 5/9. °C to °F: (°C × 9/5) + 32. °C to K: °C + 273.15. Key crossover: -40° is the same in both °F and °C. Body temp: 98.6°F = 37°C. Water boils: 212°F = 100°C. Water freezes: 32°F = 0°C.
Temperature Reference Points
| Reference | °F | °C | K |
|---|---|---|---|
| Absolute Zero | -459.67 | -273.15 | 0 |
| F/C Crossover | -40 | -40 | 233.15 |
| Water Freezes | 32 | 0 | 273.15 |
| Body Temperature | 98.6 | 37.0 | 310.15 |
| Water Boils | 212 | 100 | 373.15 |
Water boiling point varies with altitude. At 5,000 ft elevation, water boils at 203°F (95°C). At 10,000 ft: 194°F (90°C). This affects cooking times significantly.
Frequently Asked Questions
What is Kelvin and why does science use it?
Kelvin starts at absolute zero — the coldest possible temperature where all molecular motion stops. This makes it an absolute scale: 200K is exactly twice as hot as 100K in terms of thermal energy. Celsius and Fahrenheit can't make that claim because their zeros are arbitrary. Gas laws (PV=nRT), thermodynamics, and radiation physics all require absolute temperature to produce correct results.
Why does the US still use Fahrenheit?
Historical inertia. Fahrenheit was established in the US before the metric system was developed. Interestingly, Fahrenheit has finer resolution for everyday temperatures — the 0-100°F range covers typical weather conditions (-18°C to 38°C), giving more meaningful whole-number distinctions than Celsius for daily life. However, for science, cooking, and global communication, Celsius is far more practical.
How do I quickly estimate °F to °C in my head?
Subtract 30, then divide by 2. This gives a rough estimate within ~2°C for everyday temperatures. Example: 72°F → (72-30)/2 = 21°C (actual: 22.2°C). For °C to °F: double it, add 30. Example: 25°C → (25×2)+30 = 80°F (actual: 77°F). Not exact, but useful for travel and quick mental estimates.