Temperature Converter

Use the formula: °C = (°F - 32) × 5/9. First subtract 32, then multiply by 5/9 (or divide by 1.8). Example: 98.6°F → (98.6 - 32) × 5/9 = 66.6 × 0.556 = 37°C. Quick estimate: subtract 30, divide by 2.

Use the formula: °F = (°C × 9/5) + 32. Multiply by 9/5 (or 1.8), then add 32. Example: 25°C → (25 × 1.8) + 32 = 45 + 32 = 77°F. Quick estimate: double, then add 30.

Kelvin is the absolute temperature scale used in science. It starts at absolute zero (0K), the coldest possible temperature where all molecular motion stops. To convert: K = °C + 273.15. It's used in physics, chemistry, and astronomy because it avoids negative values and is proportional to thermal energy.

Absolute zero is the lowest possible temperature: 0 Kelvin, -273.15°C, or -459.67°F. At this temperature, atoms would have minimum energy and stop moving entirely. It cannot actually be reached, only approached. The coldest temperature ever achieved in a lab was about 100 picoKelvin.

Fahrenheit was developed in 1724 by Daniel Fahrenheit and adopted by English-speaking countries. Celsius was developed in 1742 by Anders Celsius and adopted by most of the world. The US retained Fahrenheit due to infrastructure and cultural inertia, while other countries switched to the metric system.

-40 degrees is the same on both scales: -40°F = -40°C. This is the only point where the two scales intersect. You can verify: (-40 - 32) × 5/9 = -72 × 5/9 = -40.

Normal body temperature is approximately 98.6°F (37°C), though it varies. Normal range is 97°F-99°F (36.1°C-37.2°C). It's typically lowest in the morning and highest in the late afternoon. A fever is generally considered 100.4°F (38°C) or higher.

Water freezes: 32°F / 0°C / 273.15K. Water boils: 212°F / 100°C / 373.15K. Room temperature: ~68-72°F / 20-22°C. Human body: 98.6°F / 37°C. Hot summer day: ~90°F / 32°C. Cold winter day: ~32°F / 0°C. Absolute zero: -459.67°F / -273.15°C / 0K.