Temperature Converter
Enter a temperature in any scale to instantly see the equivalent in Celsius, Fahrenheit, Kelvin, and Rankine. Type in any field and all others update automatically.
Common Reference Temperatures
| Description | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20–22 | 68–72 | 293–295 |
| Normal body temperature | 37 | 98.6 | 310.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Oven — low heat | 150 | 302 | 423.15 |
| Oven — moderate heat | 175 | 350 | 448.15 |
| Steel melts | 1,370 | 2,500 | 1,643 |
Temperature Conversion Formulas
| Convert From | Convert To | Formula |
|---|---|---|
| Celsius | Fahrenheit | °F = (°C × 9/5) + 32 |
| Fahrenheit | Celsius | °C = (°F − 32) × 5/9 |
| Celsius | Kelvin | K = °C + 273.15 |
| Kelvin | Celsius | °C = K − 273.15 |
| Fahrenheit | Kelvin | K = (°F + 459.67) × 5/9 |
| Kelvin | Rankine | °R = K × 9/5 |
| Rankine | Fahrenheit | °F = °R − 459.67 |
About the Temperature Scales
Celsius (°C)
Developed by Anders Celsius in 1742, the Celsius scale sets the freezing point of water at 0°C and the boiling point at 100°C (at sea level). It is the standard scale in most countries and in scientific work worldwide.
Fahrenheit (°F)
Proposed by Daniel Gabriel Fahrenheit in 1724, this scale places the freezing point of water at 32°F and the boiling point at 212°F. It remains the primary temperature scale in the United States for everyday use.
Kelvin (K)
The Kelvin scale is the SI base unit for temperature. It starts at absolute zero — the coldest possible temperature (0 K = −273.15°C), where molecular motion theoretically stops. Kelvin uses the same degree size as Celsius; it has no negative values. Kelvin is used extensively in physics, chemistry, and astronomy.
Rankine (°R)
The Rankine scale is an absolute scale like Kelvin, but uses the Fahrenheit degree size. Its zero point is absolute zero (0°R = −459.67°F). Rankine is primarily used in some engineering applications in the United States, particularly in thermodynamics.
Quick Mental Conversions
- °C to °F (approximate): Double the Celsius value, then add 30. (e.g., 20°C → 40 + 30 = 70°F; actual = 68°F)
- °F to °C (approximate): Subtract 30, then halve. (e.g., 70°F → 70 − 30 = 40 ÷ 2 = 20°C; actual = 21.1°C)
- Exact crossover: −40°C = −40°F. These two scales are identical at this temperature.
Frequently Asked Questions
What is absolute zero?
Absolute zero (0 K, −273.15°C, −459.67°F) is the theoretical lowest possible temperature, at which a system has minimum thermodynamic energy. It is approached but never actually reached in practice. The coldest recorded natural temperature in the universe is the Boomerang Nebula at about 1 K.
Why does the US use Fahrenheit while most of the world uses Celsius?
Fahrenheit was the dominant scale in the English-speaking world until the 20th century. When most countries adopted the metric system, they switched to Celsius. The United States never fully adopted the metric system, so Fahrenheit remains in everyday use there, though Celsius is used in scientific and medical contexts.
Does water always boil at 100°C?
Only at standard atmospheric pressure (1 atm / 101.3 kPa / sea level). At higher altitudes, where atmospheric pressure is lower, water boils at a lower temperature — about 95°C at 1,500 meters (5,000 feet), and 90°C at 3,000 meters (10,000 feet). This affects cooking times significantly.
