Temperature Converter

How it works

Temperature is unique among unit conversions in that the formulas are not just a multiplicative scale — there's an offset. Celsius (°C) is defined so water freezes at 0° and boils at 100° (at sea level). Fahrenheit (°F) puts the freezing point of water at 32° and boiling at 212° — a 180° gap, vs Celsius's 100° gap. Kelvin (K) is the SI absolute scale: 0 K is absolute zero, the lowest possible temperature, equal to −273.15 °C.

The formulas: °F = °C × 9/5 + 32. °C = (°F − 32) × 5/9. K = °C + 273.15. For mental approximation, °C ≈ (°F − 30) / 2 — close enough for weather contexts. To check: 70°F → ~20°C, 40°F → ~5°C, 90°F → ~30°C.

Critical reference points to remember: 0°C = 32°F (water freezes); 100°C = 212°F (water boils at sea level); 37°C ≈ 98.6°F (human body); 20–22°C ≈ 68–72°F (room temperature); −40°C = −40°F (only point where the two scales coincide).

Kelvin is used in science, especially for thermodynamics, gas laws, and any equation where ratios of temperature matter. You can't have a 0 K cap — anything physical is a few K above absolute zero. Stars are described in K (the Sun's surface is ~5,778 K).

A common mistake is treating temperature differences as if they're absolute temperatures. A 10°C *change* is the same as a 10 K change, but you can't say "20°C is twice as warm as 10°C" — that's only true on the Kelvin scale. For most everyday purposes the distinction doesn't matter, but for thermodynamic ratios it absolutely does.