How to Use the Temperature Converter
This tool supports instant conversion between Celsius (°C), Fahrenheit (°F), and Kelvin (K). Select the input temperature unit from the dropdown, enter a value, and the corresponding values in the other two units are displayed instantly below.
Unlike length and weight, temperature conversion is not a simple ratio — it requires specific formulas. This tool uses Celsius as the intermediate reference to ensure accurate results.
Temperature Conversion Formulas
Celsius ↔ Fahrenheit
°F = °C × 9/5 + 32
°C = (°F − 32) × 5/9
Celsius ↔ Kelvin
K = °C + 273.15
°C = K − 273.15
Fahrenheit ↔ Kelvin
K = (°F − 32) × 5/9 + 273.15
°F = (K − 273.15) × 9/5 + 32
Common Temperature Reference
| Scenario | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute Zero | −273.15 | −459.67 | 0 |
| Freezing Point of Water | 0 | 32 | 273.15 |
| Comfortable Room Temp. | 22 ~ 26 | 71.6 ~ 78.8 | 295.15 ~ 299.15 |
| Normal Body Temperature | 37 | 98.6 | 310.15 |
| Fever Threshold | 38 | 100.4 | 311.15 |
| Boiling Point of Water | 100 | 212 | 373.15 |
| Common Oven Temperature | 180 | 356 | 453.15 |
Temperature Conversion Examples
Body Temperature
37°C (normal) = 98.6°F = 310.15 K
38.5°C (fever) = 101.3°F = 311.65 K
Weather Temperature
0°C (freezing) = 32°F = 273.15 K
35°C (hot weather) = 95°F = 308.15 K
−10°C (cold snap) = 14°F = 263.15 K
Cooking Temperature
180°C (baking) = 356°F
200°C (high-temp roasting) = 392°F
Notes
- Kelvin has no negative values：The Kelvin scale starts at absolute zero, so there are theoretically no temperatures below 0 K. Absolute zero (0 K = −273.15°C) is the lowest possible temperature in the universe.
- Celsius and Fahrenheit intersect at −40 degrees: −40°C = −40°F. This is the only temperature where the two scales are equal.
- Kelvin is the SI unit of thermodynamic temperature, mainly used in scientific research and rarely in daily life.
- The Fahrenheit scale is primarily used in the United States and a few other regions. Most countries worldwide use the Celsius scale.
Frequently Asked Questions
How do I quickly convert Celsius to Fahrenheit in my head?
The formula is °F = °C × 9/5 + 32. Quick mental math: multiply the Celsius temperature by 2 and add 30 to get an approximate Fahrenheit value. For example, 25°C × 2 + 30 = 80°F (exact: 77°F) — close enough for everyday estimates.
What is absolute zero? Why can't Kelvin be negative?
Absolute zero (0 K = −273.15°C = −459.67°F) is the theoretically lowest possible temperature, where molecular motion nearly stops. The Kelvin scale is designed with this as its zero point, so negative values do not exist. Laboratories have cooled matter to within fractions of a degree above absolute zero, but it can never truly be reached.
What is normal body temperature? What temperature indicates a fever?
Normal body temperature is approximately 37°C (98.6°F). Generally, an axillary temperature above 37.5°C or an ear/forehead temperature above 38°C (100.4°F) is considered a fever. However, body temperature can vary by measurement site, time of day, and individual.
Why does the United States use Fahrenheit instead of Celsius?
The Fahrenheit scale was proposed by German physicist Daniel Gabriel Fahrenheit in 1724, before the Celsius scale (1742) gained widespread adoption. The US chose to retain its traditional unit system rather than adopt the metric system, so Fahrenheit remains the primary temperature unit there.