Temperature Converter
Convert between Celsius, Fahrenheit and Kelvin instantly.
How to Convert Between Temperature Scales
Temperature conversion is essential when cooking from international recipes, travelling between countries, reading scientific literature, or interpreting weather forecasts. There are three main temperature scales in use today: Celsius (°C), Fahrenheit (°F), and Kelvin (K). Celsius is used in most of the world for everyday temperature, Fahrenheit is used primarily in the United States, and Kelvin is the scientific standard used in physics and chemistry.
Temperature Conversion Formulas
| Convert | Formula | Example |
|---|---|---|
| Celsius → Fahrenheit | °F = (°C × 9/5) + 32 | 100°C = 212°F |
| Fahrenheit → Celsius | °C = (°F − 32) × 5/9 | 98.6°F = 37°C |
| Celsius → Kelvin | K = °C + 273.15 | 0°C = 273.15 K |
| Kelvin → Celsius | °C = K − 273.15 | 300 K = 26.85°C |
| Fahrenheit → Kelvin | K = (°F − 32) × 5/9 + 273.15 | 32°F = 273.15 K |
Key Temperature Reference Points
| Temperature | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | −273.15°C | −459.67°F | 0 K |
| Water freezes | 0°C | 32°F | 273.15 K |
| Cold winter day | −10°C | 14°F | 263.15 K |
| Room temperature | 20–22°C | 68–72°F | 293–295 K |
| Body temperature | 37°C | 98.6°F | 310.15 K |
| Hot summer day | 35°C | 95°F | 308.15 K |
| Water boils | 100°C | 212°F | 373.15 K |
| Oven (moderate) | 180°C | 356°F | 453.15 K |
Celsius vs Fahrenheit — Understanding the Difference
The Celsius scale sets its zero point at the freezing point of water and 100°C at the boiling point (at standard atmospheric pressure). The Fahrenheit scale, developed by Daniel Gabriel Fahrenheit in the early 18th century, sets 32°F as the freezing point and 212°F as the boiling point of water — a span of 180 degrees vs 100 degrees in Celsius.
There is one temperature where both scales agree: −40°C = −40°F. This is a useful fact for quick orientation. Above −40°, Fahrenheit numbers are always higher than the equivalent Celsius temperature.
To roughly convert Celsius to Fahrenheit in your head: double the Celsius value and add 30. Example: 20°C → (20 × 2) + 30 = 70°F (actual: 68°F). For Fahrenheit to Celsius: subtract 30 and halve it. Example: 80°F → (80 − 30) / 2 = 25°C (actual: 26.7°C). These are approximations but useful for everyday intuition.
What is Kelvin and When is it Used?
Kelvin is the base unit of temperature in the International System of Units (SI). Unlike Celsius and Fahrenheit, Kelvin has no degree symbol — you write "300 K" not "300°K." The Kelvin scale starts at absolute zero (0 K = −273.15°C), the theoretical point at which all molecular motion stops. Kelvin is used in physics, chemistry, astronomy, and engineering — particularly wherever thermodynamic calculations are involved. For example, the colour temperature of light sources (like LED bulbs rated at 2700K or 6500K) is expressed in Kelvin.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8), then add 32. Formula: °F = (°C × 1.8) + 32. Example: 25°C × 1.8 = 45, plus 32 = 77°F. Common benchmarks: 0°C = 32°F, 20°C = 68°F, 37°C = 98.6°F, 100°C = 212°F.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit value, then multiply by 5/9. Formula: °C = (°F − 32) × 5/9. Example: 98.6°F − 32 = 66.6, × 5/9 = 37°C. Common benchmarks: 32°F = 0°C, 72°F ≈ 22°C, 98.6°F = 37°C, 212°F = 100°C.
What temperature is the same in Celsius and Fahrenheit?
The only temperature where both scales give the same numerical value is −40 degrees. −40°C = −40°F. You can verify this: (−40 × 9/5) + 32 = −72 + 32 = −40.
What is normal human body temperature in Celsius and Fahrenheit?
The classic figure is 37°C (98.6°F), but this is an average — normal body temperature varies by individual, time of day, and measurement location. Recent studies suggest the average is closer to 36.6°C (97.9°F) for many people. A fever is generally defined as 38°C (100.4°F) or above.
Why does the US use Fahrenheit instead of Celsius?
The United States adopted the Fahrenheit scale in the colonial era and has not completed metrication, unlike most other countries. Fahrenheit was the dominant scale in English-speaking countries until the UK, Canada, and Australia switched to Celsius during the 1960s–70s as part of metrication programmes. The US remains one of only three countries (along with Liberia and Myanmar) that still primarily uses imperial units in everyday life.