Temperature Conversion
Convert temperature between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur scales. Used in weather forecasting, cooking, science, and HVAC engineering. See also our Celsius to Fahrenheit and Kelvin to Celsius converters.
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Popular Temperature Converters:
What is a Temperature Converter?
A temperature converter is a tool that converts values between Celsius, Fahrenheit, Kelvin, and other temperature scales. It is essential for cooking, weather interpretation, scientific research, and international travel where different temperature scales are used.
History of Temperature Measurement
Daniel Fahrenheit developed the mercury thermometer and his temperature scale in 1714. Anders Celsius proposed the centigrade scale in 1742, later renamed Celsius. Lord Kelvin introduced the absolute temperature scale in 1848, starting at absolute zero where all molecular motion ceases.
About This Temperature Converter
This temperature converter supports Celsius, Fahrenheit, Kelvin, Rankine, Reaumur, and Triple point of water. Unlike other unit converters, temperature conversion requires formulas with offsets rather than simple multiplication factors.
Understanding Temperature Measurement and Conversion
Temperature measures the average kinetic energy of particles in a substance — how hot or cold something is. Unlike most unit conversions which involve simple multiplication, temperature conversion requires both multiplication and addition (or subtraction) because temperature scales have different zero points. Zero degrees Celsius, zero degrees Fahrenheit, and zero kelvin all represent different physical conditions, making temperature conversion uniquely challenging among everyday measurements.
Three temperature scales dominate: Celsius (°C, used by most of the world and in science), Fahrenheit (°F, used in the US and some Caribbean nations for daily weather and cooking), and Kelvin (K, the SI absolute scale used in science). Celsius sets 0° at water's freezing point and 100° at its boiling point. Fahrenheit sets 32° at freezing and 212° at boiling. Kelvin starts at absolute zero (−273.15°C) — the coldest possible temperature where all molecular motion stops.
Temperature conversion is needed daily: interpreting weather forecasts when traveling internationally, following cooking recipes from other countries, understanding scientific data, and working in medicine (body temperature is 98.6°F = 37°C). The non-linear relationship between scales (offset + scaling) means you cannot simply multiply by a single factor as with length or weight.
How to Convert Between Temperature Scales (Step-by-Step)
Temperature conversion uses formulas rather than simple multiplication factors because the scales have different zero points. Here are the key conversion formulas and how to apply them:
- Celsius to Fahrenheit: °F = (°C × 9/5) + 32. Multiply by 1.8, then add 32.
- Fahrenheit to Celsius: °C = (°F − 32) × 5/9. Subtract 32, then multiply by 0.5556.
- Celsius to Kelvin: K = °C + 273.15. Simply add 273.15 (same degree size, shifted zero).
- Kelvin to Celsius: °C = K − 273.15. Simply subtract 273.15.
- Fahrenheit to Kelvin: K = (°F − 32) × 5/9 + 273.15. Convert to Celsius first, then add 273.15.
Essential Temperature Conversion Formulas
Unlike other unit conversions, temperature requires formulas with offsets, not just multiplication factors:
- °F = (°C × 9/5) + 32 or °F = (°C × 1.8) + 32
- °C = (°F − 32) × 5/9 or °C = (°F − 32) / 1.8
- K = °C + 273.15 (Kelvin from Celsius)
- °C = K − 273.15 (Celsius from Kelvin)
- K = (°F − 32) × 5/9 + 273.15 (Kelvin from Fahrenheit)
- °R = °F + 459.67 (Rankine from Fahrenheit)
- Δ1°C = Δ1.8°F (for temperature differences only)
- −40°C = −40°F (the crossover point where both scales are equal)
Worked Examples — Temperature Conversions
Example 1: Normal body temperature is 98.6°F. Convert to Celsius and Kelvin.
Solution:
°C = (98.6 − 32) × 5/9 = 66.6 × 0.5556 = 37.0°C.
K = 37.0 + 273.15 = 310.15 K.
Answer: 98.6°F = 37.0°C = 310.15 K.
Example 2: An oven recipe says 180°C. What Fahrenheit setting should you use?
Solution:
°F = (180 × 9/5) + 32 = 324 + 32 = 356°F.
Most ovens would round to 350°F (a standard baking temperature).
Answer: 180°C = 356°F (use 350°F on most American ovens).
Example 3: Liquid nitrogen boils at −196°C. Express in Fahrenheit and Kelvin.
Solution:
°F = (−196 × 1.8) + 32 = −352.8 + 32 = −320.8°F.
K = −196 + 273.15 = 77.15 K.
Answer: Liquid nitrogen: −196°C = −320.8°F = 77.15 K.
Example 4: A weather report says tomorrow will be 95°F. Is that hot in Celsius?
Solution:
°C = (95 − 32) × 5/9 = 63 × 0.5556 = 35°C.
35°C is very hot — a heat advisory level in many countries.
Answer: 95°F = 35°C (very hot; most people find temperatures above 30°C uncomfortable).
Example 5: Absolute zero is 0 K. Express in Celsius and Fahrenheit.
Solution:
°C = 0 − 273.15 = −273.15°C.
°F = (−273.15 × 1.8) + 32 = −491.67 + 32 = −459.67°F.
Answer: Absolute zero: 0 K = −273.15°C = −459.67°F (coldest possible temperature).
Quick Reference — Common Temperature Conversions
Important temperature points across all three major scales.
| From | To |
|---|---|
| Absolute zero | 0 K = −273.15°C = −459.67°F |
| Liquid nitrogen | 77 K = −196°C = −320.8°F |
| Water freezes | 273.15 K = 0°C = 32°F |
| Cold day | 263 K = −10°C = 14°F |
| Room temperature | 293 K = 20°C = 68°F |
| Body temperature | 310 K = 37°C = 98.6°F |
| Hot day | 313 K = 40°C = 104°F |
| Water boils | 373.15 K = 100°C = 212°F |
| Oven baking | 453 K = 180°C = 356°F |
| Broiling | 533 K = 260°C = 500°F |
| Paper ignites | 506 K = 233°C = 451°F |
| Iron melts | 1,811 K = 1,538°C = 2,800°F |
| −40° crossover | 233 K = −40°C = −40°F |
| Sun surface | 5,778 K = 5,505°C = 9,941°F |
Celsius, Fahrenheit, and Kelvin: Three Temperature Scales
The Celsius scale (formerly centigrade) was developed by Anders Celsius in 1742 and sets 0° at the freezing point of water and 100° at its boiling point (both at standard atmospheric pressure). This makes Celsius intuitive for everyday life: below 0 means ice, above 100 means steam. Each degree represents 1/100 of the temperature difference between these fixed points. Celsius is used for daily weather, cooking, and general temperature communication in most of the world.
The Fahrenheit scale was developed by Daniel Fahrenheit in 1724. He set 0°F at the temperature of a specific brine solution (the coldest he could reproducibly create), 32°F at water's freezing point, and 212°F at water's boiling point. This gives 180 divisions between freezing and boiling (vs Celsius's 100), making each Fahrenheit degree smaller. The scale puts most weather temperatures in a convenient 0-100 range — 0°F is very cold and 100°F is very hot — which some argue makes it more intuitive for daily weather.
The Kelvin scale is the SI thermodynamic temperature scale, starting at absolute zero — the temperature at which all thermal motion ceases. One kelvin has the same magnitude as one degree Celsius (they differ only by their zero point: 0 K = −273.15°C). Kelvin is essential in science because many physical laws (ideal gas law PV = nRT, blackbody radiation, thermodynamic efficiency) require absolute temperature. Negative kelvin does not exist in classical thermodynamics, making it the only scale guaranteed to have no negative values.
Where Temperature Conversion Matters
International Travel
A weather forecast of 35°C means "dangerously hot" (95°F), while 0°C means freezing. Americans traveling to metric countries (nearly everywhere) need mental conversion skills. Knowing that 20°C = 68°F (comfortable) and 30°C = 86°F (hot) provides useful benchmarks.
Cooking & Baking
Recipes from the UK/Europe use Celsius; American recipes use Fahrenheit. An oven at 180°C = 356°F (use 350°F). At high temperatures the scales diverge more: 230°C = 446°F (use 450°F). Meat doneness temperatures also differ between recipe sources.
Medicine & Healthcare
Body temperature is 37°C = 98.6°F. A fever is above 38°C (100.4°F). Hospital equipment may use either scale. Medication storage requirements (e.g., "store between 2-8°C") need conversion for Fahrenheit thermometers (36-46°F).
Science & Engineering
Chemical reactions, material properties, and physics calculations use Kelvin or Celsius. Superconductors operate below 77 K (−196°C). Semiconductor fabrication specifies temperatures in °C. Thermodynamic efficiency calculations require Kelvin.
HVAC & Thermostat Settings
Thermostat recommendations differ by country unit system. "Set to 68°F" = "Set to 20°C." Energy savings of "turning down 2 degrees" means different things: 2°F = 1.1°C, 2°C = 3.6°F. International HVAC standards require conversion.
Industrial Processes
Steel treatment temperatures, plastic molding temperatures, and food processing temperatures use different scales by region. A steel tempering temperature of 400°C (752°F) must be precisely controlled — errors from conversion mistakes damage products.
Common Mistakes in Temperature Conversion
The most critical error is forgetting the offset. People sometimes try to convert temperature by multiplying alone (like other units): "20°C × 1.8 = 36°F" is WRONG. The correct answer is (20 × 1.8) + 32 = 68°F. The 32-degree offset matters enormously. Another common mistake is applying the conversion formula to temperature differences. If a room heats up by 10°C, the Fahrenheit change is 10 × 1.8 = 18°F (NO plus-32 needed for differences). The offset only applies to absolute temperatures, not to changes in temperature. Finally, confusing Celsius and Kelvin in scientific work can be dangerous: mixing them in gas law calculations gives wildly wrong results.
Why Temperature Conversion Is Different From Other Units
Most unit conversions are proportional — doubling the input doubles the output. Temperature is different because the scales have different zero points. Zero degrees Celsius is not "no temperature" (absolute zero is −273.15°C). Because of this offset, the conversion function is affine (y = mx + b) rather than proportional (y = mx). This is why 0°C = 32°F (not 0°F), and why doubling the Celsius value does NOT double the Fahrenheit value. For example, 10°C = 50°F, but 20°C = 68°F (not 100°F). This non-proportional behavior makes temperature conversion less intuitive than converting meters to feet or kilograms to pounds.
Key Takeaways
- Temperature conversion uses formulas, not simple multiplication: °F = °C × 1.8 + 32.
- Key reference points: water freezes at 0°C/32°F, boils at 100°C/212°F.
- Celsius to Kelvin: just add 273.15. The degree size is identical.
- The only point where °C = °F is −40. Below that, °F gives lower numbers; above, °F gives higher numbers.
- Quick estimate C→F: double and add 30. Quick estimate F→C: subtract 30 and halve.
- For temperature DIFFERENCES (not absolute values): Δ1°C = Δ1.8°F. A 10°C rise = 18°F rise.
Metric Conversion Factor Tables for Temperature Converter
| Units to convert | Multiply By The Number | Convert as Unit |
|---|---|---|
| Fahrenheit (°F) | (°F − 32) / 1.8 | Celsius (°C) |
| Celsius (°C) | (°C × 1.8) + 32 | Fahrenheit (°F) |
| Celsius (°C) | Add 273.15 | Kelvin (K) |
| Kelvin (K) | Subtract 273.15 | Celsius (°C) |
Temperatureconverters & it's abbreviations
| Unit | Abbreviation | Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|---|---|
| kelvin | K | Celsius | °C | Fahrenheit | °F |
| Rankine | °R | Reaumur | °r | Triple point of water | - |
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8) and add 32. For example, 25°C = (25 × 1.8) + 32 = 77°F.
What is absolute zero?
Absolute zero is 0 Kelvin (−273.15°C or −459.67°F). It is the theoretical temperature where all molecular motion stops and is the lowest possible temperature.
What temperature is the same in Celsius and Fahrenheit?
−40 degrees is the same in both Celsius and Fahrenheit. This is the only point where the two scales intersect.
Why does the US use Fahrenheit?
The US adopted Fahrenheit before the metric system became widespread. Fahrenheit offers more granularity for everyday weather temperatures since its degree increments are smaller than Celsius degrees.
What is the boiling point of water in all scales?
Water boils at 100°C, 212°F, 373.15 K, 671.67°R, and 80°r (Reaumur) at standard atmospheric pressure.
Complete list of Temperature conversion units and its conversion.
- 0 Celsius [°C] = 32 Fahrenheit [°F]
celsius to fahrenheit → - 0 Celsius [°C] = 273.15 kelvin [K]
celsius to kelvin → - 0 Celsius [°C] = 491.67 Rankine [°R]
celsius to rankine →
- 32 Fahrenheit [°F] = 491.67 Rankine [°R]
fahrenheit to rankine → - 32 Fahrenheit [°F] = 0 Reaumur [°r]
fahrenheit to reaumur → - 273.15 kelvin [K] = 0 Celsius [°C]
kelvin to celsius →
- 491.67 Rankine [°R] = 0 Celsius [°C]
rankine to celsius → - 491.67 Rankine [°R] = 32 Fahrenheit [°F]
rankine to fahrenheit → - 491.67 Rankine [°R] = 273.15 kelvin [K]
rankine to kelvin →
- 0 Reaumur [°r] = 273.15 kelvin [K]
reaumur to kelvin → - 0 Reaumur [°r] = 491.67 Rankine [°R]
reaumur to rankine →
- 0 Celsius [°C] = 0 Reaumur [°r]
celsius to reaumur → - 32 Fahrenheit [°F] = 0 Celsius [°C]
fahrenheit to celsius → - 32 Fahrenheit [°F] = 273.15 kelvin [K]
fahrenheit to kelvin →
- 273.15 kelvin [K] = 32 Fahrenheit [°F]
kelvin to fahrenheit → - 273.15 kelvin [K] = 491.67 Rankine [°R]
kelvin to rankine → - 273.15 kelvin [K] = 0 Reaumur [°r]
kelvin to reaumur →
- 491.67 Rankine [°R] = 0 Reaumur [°r]
rankine to reaumur → - 0 Reaumur [°r] = 0 Celsius [°C]
reaumur to celsius → - 0 Reaumur [°r] = 32 Fahrenheit [°F]
reaumur to fahrenheit →