Instantly convert between Celsius (°C), Fahrenheit (°F), and Kelvin (K) using this free and easy converter.
The Temperature Converter instantly converts between Celsius (°C), Fahrenheit (°F), and Kelvin (K) — the three temperature scales you'll encounter in daily life, cooking, travel, science, and medicine. Simply enter a temperature and choose your units to get an immediate, accurate result.
There is exactly one temperature where Celsius and Fahrenheit are equal: −40 degrees. At −40°C = −40°F, both scales converge. This crossover point is sometimes reached in extreme Arctic or subarctic conditions and is a handy checkpoint for estimating conversions at very low temperatures.
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Multiply the Celsius value by 9/5, then add 32. Formula: °F = (°C × 9/5) + 32. Example: 25°C → (25 × 1.8) + 32 = 45 + 32 = 77°F. For a quick mental estimate, multiply by 2 and add 30.
Subtract 32 from the Fahrenheit value, then multiply by 5/9. Formula: °C = (°F − 32) × 5/9. Example: 77°F → (77 − 32) × 5/9 = 45 × 0.556 = 25°C.
Add 273.15 to the Celsius value. Formula: K = °C + 273.15. Example: 100°C = 373.15 K. To reverse: °C = K − 273.15.
Formula: °F = (K − 273.15) × 9/5 + 32. Example: 373.15 K → (373.15 − 273.15) × 1.8 + 32 = 180 + 32 = 212°F (boiling point of water).
Celsius and Fahrenheit are equal at exactly −40 degrees. At −40°C = −40°F, both scales intersect. This is a useful memory anchor: below −40, Celsius numbers are smaller in magnitude than Fahrenheit; above −40, Fahrenheit values are higher.
Absolute zero is the lowest theoretically possible temperature: 0 K = −273.15°C = −459.67°F. At this temperature, all molecular motion stops. It is the foundation of the Kelvin scale, which is why Kelvin has no negative values — nothing can be colder than absolute zero.
The Fahrenheit scale was introduced by Daniel Gabriel Fahrenheit in 1724 and became widely adopted in Britain and its colonies. When most of the world transitioned to the metric system (including Celsius) in the 20th century, the US did not formally adopt it. Today the US remains one of just a few countries that still uses Fahrenheit for everyday temperature.
The traditional standard for normal body temperature is 37°C = 98.6°F. However, research shows that average body temperature varies by individual, age, and time of day — typically ranging from 36.1°C to 37.2°C (97°F to 99°F). A fever is generally defined as above 38°C (100.4°F).