Temperature converter

The formulas

• °F → °C: (F − 32) × 5 ÷ 9
• °C → °F: C × 9 ÷ 5 + 32
• °C → K: C + 273.15
• K → °C: K − 273.15

Why three scales

Celsius is the everyday metric standard, Fahrenheit dominates in the US and a few Caribbean countries, and Kelvin is the SI absolute scale used in physics. They share the same step size for Celsius and Kelvin (1 °C = 1 K of change), but offset by 273.15. Fahrenheit's step is 9/5 of a Celsius degree, so its scale stretches across larger numbers.

Worked examples

100 °C → °F (boiling point): Apply °C × 9/5 + 32. 100 × 9/5 = 180, then 180 + 32 = 212 °F. That is the boiling point of water at sea level and a useful anchor for cooking.

98.6 °F → °C (body temperature): Apply (F − 32) × 5/9. (98.6 − 32) = 66.6, then 66.6 × 5/9 ≈ 37 °C. This is normal human core temperature and the origin of the familiar "98.6" figure.

0 K → °C (absolute zero): Apply K − 273.15. 0 − 273.15 = −273.15 °C. No object can reach this temperature in practice; it is the theoretical floor where all molecular motion would cease.

Common reference temperatures

A handful of fixed points help you build intuition across all three scales. Water freezes at 0 °C / 32 °F / 273.15 K — the most commonly memorised anchor. Normal human body temperature sits at 37 °C / 98.6 °F / 310.15 K. Water boils at sea level at 100 °C / 212 °F / 373.15 K; note that altitude lowers this — the reduced atmospheric pressure at elevation means less energy is needed to vaporise water, so pasta takes longer to cook in the mountains. A moderate oven (gas mark 6) runs at roughly 200 °C / 392 °F, useful for baking bread or roasting vegetables.

Quick mental shortcuts

• °C to °F: double and add 30 — a quick approximation accurate to within ±2 °F for typical weather temperatures.
• °F to °C: subtract 30 and halve — the reverse of the same approximation.
• −40 is the same in both scales — the one point where Celsius and Fahrenheit coincide exactly.
• 16 °C ≈ 61 °F and 28 °C ≈ 82 °F — two useful weather anchors that are easy to remember and precise enough for everyday use.

Kelvin in everyday contexts

Outside the laboratory, Kelvin appears most often in photography and lighting. Camera white balance is measured in colour temperature: 3 200 K is the warm orange glow of tungsten bulbs, 5 500 K matches natural midday sunlight, and 6 500 K represents overcast sky — the cool bluish-white that many monitors are calibrated to. In physics and chemistry, Kelvin is the required unit because many equations (gas laws, thermodynamic efficiency, blackbody radiation) break down if you insert negative values. In practice you will never encounter a negative Kelvin reading; values below 0 K are physically meaningless.

Which scale to use

For cooking, weather forecasts, and medical readings, use Celsius if you are in most of the world, or Fahrenheit if you are in the United States or following a US recipe. Both work fine for everyday life; the choice is mostly cultural convention. Use Kelvin for scientific work — chemistry, physics, engineering thermodynamics, and astrophysics all require it because equations rely on absolute temperature values. When in doubt, convert to whichever scale your audience expects, and use the calculator above to verify.