Instantly convert Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Accurate, simple, and perfect for science, cooking, or travel.
Comparing slopes of Celsius, Fahrenheit, and Kelvin across -273.15°C to 1000°C.
At its core, temperature is a measure of the average kinetic energy of the molecules in a substance. When things get hotter, their molecules move faster; when they cool down, molecular motion slows. While this physical reality is the same everywhere in the universe, humans have invented different "languages" (scales) to measure it, depending on where they live or what work they do.
| Scale | Used In | Best For |
|---|---|---|
| Celsius (°C) | Most of the world, Science | Standard global communication, water-based activities. |
| Fahrenheit (°F) | USA, Caribbean | Weather forecasting (finer detail), baking in US ovens. |
The US sticks to Fahrenheit largely due to historical precedent and the feeling that it offers more precision for air temperature without using decimals.
Scientists prefer Kelvin because it is an "absolute" scale. It doesn't start at an arbitrary point like freezing water; it starts at Absolute Zero (0K), the lowest possible temperature in the universe.
Example:
The surface of the Sun is approximately 5,778K. Liquid nitrogen boils at a chilly 77K.
| Reference | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute Zero | -273.15°C | -459.67°F | 0K |
| Water Freezes | 0°C | 32°F | 273.15K |
| Room Temp | 20°C | 68°F | 293.15K |
| Body Temp | 37°C | 98.6°F | 310.15K |
| Water Boils | 100°C | 212°F | 373.15K |
| Parity Point | -40°C | -40°F | 233.15K |
Multiply by 1.8 (9/5) and add 32. The ratio 9/5 exists because Fahrenheit has 180 degrees between freezing/boiling, while Celsius has only 100.
°F = (°C × 9/5) + 32
°C = (°F - 32) × 5/9
The simplest conversion. The "step" size is identical; you just shift the starting point by 273.15 degrees.
K = °C + 273.15
°C = K - 273.15
It feels difficult because the scales don't share a zero point (0°C ≠ 0°F) and they grow at different rates (1°C change is nearly double a 1°F change).
Need a rough estimate? Subtract 30 and divide by 2.
Example: 86°F. 86 - 30 = 56. 56 / 2 = 28°C. (Actual is 30°C—close enough for deciding what to wear!)
Absolute zero (-273.15°C) is the theoretical limit where all molecular motion ceases. You cannot get colder than this.
This is the "parity point" where the different starting points and growth rates of the two scales intersect mathematically.
39°C equals 102.2°F. This is a significant fever indicating the body is fighting infection. Consult a medical professional if it persists.
180°C converts to 356°F. Most US recipes round this to 350°F.
All conversions utilize ISO 80000-5 standard formulas. Results are mathematically precise to the displayed decimal places. Boiling points assume standard atmospheric pressure at sea level.
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