Temperature Converter
Convert temperature between Celsius, Fahrenheit, Kelvin, and Rankine instantly. See formulas, real-world references, and live conversions. Free online temperature converter.
celsius
fahrenheit
kelvin
rankine
Conversion Formulas
(°C × 9/5) + 32°C + 273.15(°C + 273.15) × 9/5| Reference Point | °C | °F | K | °R | Action |
|---|---|---|---|---|---|
| Absolute Zero | -273.15 | -459.67 | 0 | 0 | |
| Liquid Nitrogen | -195.79 | -320.42 | 77.36 | 139.25 | |
| Dry Ice (CO₂) | -78.5 | -109.3 | 194.65 | 350.37 | |
| Water Freezes | 0 | 32 | 273.15 | 491.67 | |
| Cold Day | -10 | 14 | 263.15 | 473.67 | |
| Room Temperature | 20 | 68 | 293.15 | 527.67 | |
| Body Temperature | 37 | 98.6 | 310.15 | 558.27 | |
| Fever | 38.5 | 101.3 | 311.65 | 560.97 | |
| Hot Day | 40 | 104 | 313.15 | 563.67 | |
| Water Boils | 100 | 212 | 373.15 | 671.67 | |
| Oven (moderate) | 175 | 347 | 448.15 | 806.67 | |
| Wood ignites | 300 | 572 | 573.15 | 1031.67 | |
| Surface of the Sun | 5505 | 9941 | 5778 | 10400 |
Visual Thermometer
High fever - consult a doctor
Fever Checker
Is this temperature a fever?
✅ Normal temperature
37°C / 98.6°F
Within the normal range of 36.1°C to 37.2°C.
For informational purposes only. Always consult a qualified healthcare professional for medical advice.
Popular Transitions
Temperature is one of the most frequently converted measurements in everyday life - whether you are checking if a recipe calls for 180°C or 350°F, understanding a weather forecast from a foreign country, converting a patient's fever reading, or working with scientific data in Kelvin. This free online temperature converter shows all four major temperature scales simultaneously - Celsius, Fahrenheit, Kelvin, and Rankine. It displays the exact conversion formulas with your values substituted in, features a visual animated thermometer, includes a fever checker with health guidance, and provides a real-world temperature reference table. All conversions are instant, ad-free, and completely private.
How to Convert Temperatures
- Enter your temperature value in the input field
- Select your starting scale from the dropdown (Celsius, Fahrenheit, Kelvin, or Rankine)
- All four scales update simultaneously in the output cards
- Click any output card to make that scale the new input reference
- Use the Fever Checker for body temperature health guidance
- See the exact formula used in the Conversion Formulas panel
The Four Temperature Scales
- Celsius (°C) - the world standard for everyday temperature. Water freezes at 0°C and boils at 100°C at sea level. Used in all countries except the US for weather, cooking, and science communication.
- Fahrenheit (°F) - the US standard for everyday temperature. Water freezes at 32°F and boils at 212°F. Still standard in the US for weather forecasts and cooking.
- Kelvin (K) - the SI base unit of temperature. Starts at absolute zero (0 K = −273.15°C). Used in all scientific contexts because it has no negative values. Uses the same degree size as Celsius.
- Rankine (°R) - an absolute scale like Kelvin but based on the Fahrenheit degree. Used in some engineering applications in the US. 0°R = 0 K = absolute zero. 491.67°R = 0°C = freezing point of water.
Key Temperature Reference Points
There are several key anchor points every person should know to orient themselves in both systems. Absolute zero is the lowest theoretical temperature where all atomic movement stops (−273.15°C or −459.67°F). Water freezes at 0°C (32°F) and boils at 100°C (212°F) under standard conditions. Comfortable room temperature is generally around 20°C to 22°C (68°F to 72°F). Normal human body temperature is approximately 37°C (98.6°F).
The Quick Mental Conversion Trick
To quickly estimate Celsius to Fahrenheit in your head, double the Celsius value and add 30. For example 20°C × 2 = 40 + 30 = 70°F (actual is 68°F - close enough for most purposes). Going the other way: subtract 30 from Fahrenheit then halve it. These are not exact but are useful for quick mental estimates when traveling.
Key Features
- All four scales shown simultaneously (Celsius, Fahrenheit, Kelvin, Rankine)
- Visual animated thermometer with color coding
- Exact conversion formulas with your current value substituted in
- Fever Checker with health guidance
- Real-world temperature reference table with 13 reference points
- 12 popular quick-conversion cards
- Conversion history
- Below-absolute-zero validation
- Works on all devices including mobile
- 100% free - no signup, no account, no data uploaded
100% Free & 100% Private
All processing happens entirely in your browser. We never upload your data to any server. No signup, no account, no hidden fees. Just free, secure tools.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8) and then add 32. Formula: °F = (°C × 9/5) + 32. Example: 100°C = (100 × 1.8) + 32 = 212°F.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature then multiply by 5/9. Formula: °C = (°F − 32) × 5/9. Example: 98.6°F = (98.6 − 32) × 5/9 = 37°C.
What is absolute zero in Celsius and Fahrenheit?
Absolute zero is −273.15°C or −459.67°F or 0 Kelvin. It is the lowest theoretically possible temperature - the point at which all thermal motion of atoms ceases.
What temperature is the same in Celsius and Fahrenheit?
−40° is the point where Celsius and Fahrenheit are exactly equal. −40°C = −40°F. This is the only temperature where the two scales intersect.
What is normal human body temperature in Celsius and Fahrenheit?
Normal body temperature is approximately 37°C or 98.6°F. The normal range is 36.1°C to 37.2°C (97°F to 99°F). A temperature above 38°C (100.4°F) is generally considered a fever.
What is the difference between Kelvin and Celsius?
Kelvin and Celsius use the same scale size - a difference of 1°C equals a difference of 1 K. The difference is where zero is: 0°C = 273.15 K. Kelvin starts at absolute zero, so there are no negative Kelvin temperatures. To convert: K = °C + 273.15.
What is the Rankine scale?
The Rankine scale is an absolute temperature scale like Kelvin but based on the Fahrenheit degree. 0°R is absolute zero, and one Rankine degree equals one Fahrenheit degree. It is used in some engineering fields in the United States. 0°C = 491.67°R and 32°F = 491.67°R.
Is this temperature converter free?
Yes, completely free with no account required. All conversions happen in your browser instantly. No data is sent to any server.
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