Free Temperature Converter Online - Celsius, Fahrenheit & Kelvin
Type in any field — Celsius, Fahrenheit, or Kelvin — and all other scales update instantly.
Usage Examples
Click any example to load it into the converter
Boiling point of water
100°C = 212°F = 373.15 K
Freezing point of water
0°C = 32°F = 273.15 K
Normal human body temperature
37°C = 98.6°F = 310.15 K
Normal body temperature in Fahrenheit
98.6°F = 37°C = 310.15 K
Absolute zero — the lowest possible temperature
0 K = −273.15°C = −459.67°F
Comfortable room temperature
20°C = 68°F = 293.15 K
How to Use Temperature Converter
Type in Any Field
Enter a temperature in Celsius, Fahrenheit, or Kelvin. All three scales update in real time as you type.
Adjust Precision
Choose the number of decimal places (0–4) to control rounding. Kelvin and Fahrenheit values recalculate instantly.
Copy or Explore Examples
Use the copy button on each card to grab the value. Click any example below to auto-fill the converter.
Frequently Asked Questions
Basics
How do I convert Celsius to Fahrenheit?
Use the formula °F = (°C × 9/5) + 32. For example, 100°C = 100 × 9/5 + 32 = 180 + 32 = 212°F. This is the boiling point of water at standard pressure. The 9/5 ratio means each Celsius degree equals 1.8 Fahrenheit degrees. The +32 offset accounts for the fact that water freezes at 0°C but 32°F. This temperature converter calculates this instantly — just type a Celsius value and the Fahrenheit field updates in real time with your chosen decimal precision.
How do I convert Fahrenheit to Celsius?
Use the formula °C = (°F − 32) × 5/9. For example, 98.6°F = (98.6 − 32) × 5/9 = 66.6 × 5/9 = 37°C, which is normal human body temperature. The subtraction of 32 removes the offset between the freezing points, then multiplying by 5/9 converts Fahrenheit degrees into the larger Celsius degrees. This temperature converter handles the math automatically — enter any Fahrenheit value and Celsius and Kelvin update immediately.
What is absolute zero?
Absolute zero is the lowest possible temperature in the universe: 0 Kelvin, which equals −273.15°C or −459.67°F. At this temperature, all molecular motion theoretically stops, and a system has the minimum possible energy. It is impossible to reach absolute zero in practice, but scientists have cooled matter to within billionths of a Kelvin. The Kelvin scale starts at absolute zero, making it essential for scientific calculations in thermodynamics, cryogenics, and physics where proportional relationships between temperature and energy are needed.
Why does Kelvin not use degrees?
Kelvin is an absolute thermodynamic temperature scale, not a relative one. Unlike Celsius and Fahrenheit, which are defined by arbitrary reference points (water freezing/boiling), Kelvin starts at absolute zero — the theoretical absence of all thermal energy. Because it measures an absolute quantity rather than a position on an arbitrary scale, the correct notation is "273.15 K" rather than "273.15°K." The unit is simply "kelvin" (lowercase), and the symbol is K. One kelvin has the same magnitude as one Celsius degree, but the scales have different zero points.
Reference Points & Kelvin
At what temperature are Celsius and Fahrenheit equal?
Celsius and Fahrenheit are equal at -40 degrees. At this unique temperature, -40°C equals -40°F — the only point where the two scales intersect. You can verify this using the conversion formula: multiply -40 by 9/5 to get -72, then add 32 to return to -40. Below this crossover point, Fahrenheit readings are numerically colder than Celsius readings; above -40°, Celsius is colder. This fact is frequently used as a quick mental check for temperature converter accuracy. Try entering -40 in the Celsius or Fahrenheit card above to see it confirmed instantly.
What is the freezing point of water in all three scales?
The freezing point of water at standard atmospheric pressure is 0°C, 32°F, and 273.15 K. This is one of the most important reference points for temperature conversion. Celsius and Kelvin use the same increment size — a change of 1°C equals a change of 1 K — while Fahrenheit uses smaller increments where 1°F equals 5/9 of 1°C. Correspondingly, the boiling point of water is 100°C, 212°F, and 373.15 K. This temperature converter handles all three scales simultaneously, so you can see how any temperature relates to these key reference points in real time.
How do I convert Celsius to Kelvin?
Converting Celsius to Kelvin is the simplest temperature conversion: just add 273.15. The formula is K = °C + 273.15. For example, 0°C (freezing point) equals 273.15 K, and 100°C (boiling point) equals 373.15 K. Because the Kelvin scale starts at absolute zero, there are no negative Kelvin values — all temperatures are positive. Kelvin is the standard scientific scale used in physics, chemistry, and engineering precisely because it enables proportional calculations that are impossible with Celsius or Fahrenheit. This temperature converter applies the formula automatically as you type.
How do I convert Kelvin to Celsius?
Converting Kelvin to Celsius is equally straightforward: subtract 273.15 from the Kelvin value. The formula is °C = K − 273.15. For example, 300 K is approximately 26.85°C (a warm room temperature), and 310.15 K is 37°C (normal human body temperature). This conversion is essential when reading scientific papers, working with ideal gas law calculations, or interpreting climate data reported in Kelvin. This temperature converter performs the subtraction instantly and shows all three scales side by side with your chosen decimal precision.