Temperature Converter
Example 1
A chef in the United States follows a French recipe that states "preheat the oven to 180 °C". The chef's oven is marked in Fahrenheit. They need the correct temperature.
Solution
Converting from Celsius to Fahrenheit uses the formula °F = (°C × 9/5) + 32. For 180 °C: 180 × 9/5 = 324, then 324 + 32 = 356 °F.
Most baking recipes round 356 °F down to 350 °F for convenience, as ovens are typically calibrated in 25 or 50 degree Fahrenheit increments. The freezing point of water (0 °C = 32 °F) and boiling point (100 °C = 212 °F) serve as useful sanity checks: since 180 °C is nearly double the boiling point of water, the Fahrenheit equivalent should be well above 212 °F, which 356 °F confirms.
Answer
356 °F (typically rounded to 350 °F for cooking). 180 °C converts to 356 °F, which is a standard moderate oven temperature for baking.
Source: USDA Food Safety and Inspection Service: Oven Temperature Chart
Example 2
A scientist records a laboratory temperature of 298 K. They need the equivalent in °C and °F for an international journal that accepts both scales.
Solution
Converting from Kelvin to Celsius subtracts 273.15: °C = K − 273.15. For 298 K: 298 − 273.15 = 24.85 °C.
Then convert Celsius to Fahrenheit: °F = (24.85 × 9/5) + 32 = 76.73 °F.
Note that 298 K is approximately 25 °C (rounding to the nearest integer), which is standard room temperature in scientific contexts. Many chemistry and physics experiments specify conditions at 298 K (25 °C) as the standard reference temperature. The IUPAC standard conditions for temperature and pressure define 298.15 K (25 °C) and 100 kPa as the reference state for thermodynamic data.
Answer
24.9 °C (76.7 °F). A laboratory temperature of 298 K equals approximately 25 °C or 77 °F, which is standard room temperature used in many scientific experiments.
Source: IUPAC: Standard Conditions for Temperature and Pressure
Example 3
A tourist from the United States visits Canada and sees a weather forecast of 30 °C. They need to understand how warm that feels in Fahrenheit.
Solution
Converting from Celsius to Fahrenheit: °F = (30 × 9/5) + 32 = 86 °F.
A useful mental shortcut exists for Celsius-to-Fahrenheit conversion: double the Celsius value, subtract 10%, then add 32. For 30 °C: double to 60, subtract 10% (6) to get 54, then add 32 to reach 86 °F. This approximation is accurate within 1 °F for typical temperature ranges and can be done without a calculator. Compare with the exact formula: (30 × 9/5) + 32 = (54) + 32 = 86 °F, which gives the identical result because multiplying by 9/5 is mathematically equivalent to doubling and subtracting 10%.
Answer
86 °F. A temperature of 30 °C is a hot summer day at 86 °F. The mental shortcut of doubling °C, subtracting 10%, and adding 32 gives the same result without a calculator.
Example 4
A recipe instructs baking at 375°F. Convert to degrees Celsius and Kelvin.
Solution
K = 190.6 + 273.15 = 463.8 K.
190.6°C exceeds the Maillard browning threshold of 140°C.
Answer
375°F = 190.6°C = 463.8 K.
Published:
Updated:
References
- [1]Bureau International des Poids et Mesures (BIPM), The International System of Units (SI) – 9th Edition, 2019. https://www.bipm.org/en/publications/si-brochure
- [2]National Institute of Standards and Technology (NIST), Guide for the Use of the International System of Units (SI), 2008. https://physics.nist.gov/cuu/pdf/sp811.pdf
- [3]International Organization for Standardization, ISO 80000-5: Quantities and Units – Part 5: Thermodynamics, 2019.
Glossary
- Temperature – A physical quantity expressing the degree of hotness or coldness of a substance, measured using one of several defined scales. Temperature is a fundamental property in thermodynamics.
- Celsius (°C) – A temperature scale where 0 °C is defined as the freezing point of water and 100 °C as the boiling point at standard atmospheric pressure. Also called centigrade, it is the widely adopted temperature scale worldwide.
- Fahrenheit (°F) – A temperature scale where 32 °F is the freezing point of water and 212 °F is the boiling point. It is used officially in the United States and historically in a few other countries.
- Kelvin (K) – The SI base unit of thermodynamic temperature, where 0 K (absolute zero) is the theoretical point at which all molecular motion ceases. Temperatures in Kelvin are used in scientific research and engineering.
- Absolute zero – The lowest possible thermodynamic temperature, at which particles have minimum kinetic energy. Absolute zero is 0 K, −273.15 °C, or −459.67 °F, and is a theoretical limit never reached in practice.
- Freezing point – The temperature at which a liquid turns into a solid under standard atmospheric pressure. For water, the freezing point is 0 °C or 32 °F, though impurities and pressure changes can alter it.
- Boiling point – The temperature at which a liquid's vapour pressure equals atmospheric pressure, causing it to change to gas. The boiling point of water is 100 °C or 212 °F at sea level and decreases with altitude.
- Temperature conversion formula – The mathematical equations used to convert between temperature scales: °F = (°C × 9/5) + 32, °C = (°F − 32) × 5/9, K = °C + 273.15.
- Degree symbol – The typographic symbol (°) used before the letter C or F to denote temperature in Celsius or Fahrenheit. The Kelvin scale omits the degree symbol, using simply K.
- Heat index – A measure of how hot it feels to the human body when relative humidity is combined with air temperature. The heat index differs from actual temperature and is reported in summer weather forecasts.
How to Use?
- 1
Enter the temperature value
Type the numeric temperature into the Value field. Use the unit dropdown to select Celsius (°C), Fahrenheit (°F), or Kelvin (K).
- 2
Select the source unit
Choose the unit of your input from the dropdown next to the value field. The calculator normalises all inputs to Celsius internally, so any unit works as the source.
- 3
Review all three equivalent values
The results panel displays the equivalent temperature in Celsius, Fahrenheit, and Kelvin simultaneously. All three are always shown regardless of which unit you entered.
- 4
Check decimal precision
Results are displayed with two decimal places, sufficient for weather, cooking, medical, and most laboratory applications.
- 5
Verify against known reference points
Cross-check results against common values: water freezes at 0 °C / 32 °F / 273.15 K, body temperature is 37 °C / 98.6 °F / 310.15 K.
- 6
Use related converters
For thermal energy and heat transfer calculations, use the <a href="/calculator/energy-converter">Energy Converter</a> on this site.
Frequently Asked Questions
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For 98.6 °F: (98.6 − 32) = 66.6, times 5/9 = 37.0 °C. This formula works for any Fahrenheit temperature. A quick mental shortcut is to subtract 32, halve the result, then add about 10%. Use this converter for exact results without mental arithmetic.
Absolute zero is 0 K, −273.15 °C, or −459.67 °F. It is the lowest possible temperature where all molecular motion ceases at the classical level, leaving only quantum mechanical zero-point energy. Absolute zero is the starting point of the Kelvin scale and the foundation of the third law of thermodynamics. No physical system can reach exactly absolute zero through any finite process.
The two scales intersect at −40°, where −40 °C = −40 °F. This is the only temperature where the numeric value is the same in both scales. It is a useful reference point for quick mental conversion checks and a common trivia question in science education. Enter −40 in either unit in this converter to verify.
Kelvin is an absolute thermodynamic temperature scale, not a relative one. The degree symbol was officially removed by the 13th General Conference on Weights and Measures (CGPM) in 1967 because Kelvin is a unit of absolute temperature, not a degree of temperature. Writing “100 °K” is technically incorrect; the correct notation is “100 K” with a space between the number and the unit symbol. Celsius and Fahrenheit retain the degree symbol because they are relative scales with arbitrary zero points.
At standard atmospheric pressure (sea level), water boils at 100 °C, 212 °F, and 373.15 K. The boiling point decreases with altitude: at 1,500 metres (5,000 ft), water boils at approximately 95 °C (203 °F, 368 K). This is why cooking times and temperatures must be adjusted at high elevations.
The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in 1724 and became established in the English-speaking world through British colonial influence. The US continued using Fahrenheit after most other countries adopted the metric system and Celsius in the 19th and 20th centuries. The US considered metrication in the 1970s but the conversion was voluntary and never fully implemented. Today, the US uses Fahrenheit for everyday weather and cooking, Celsius for most scientific work, and Kelvin for thermodynamic calculations, creating a practical trilingual temperature environment.
−40 degrees. At −40°, the Celsius and Fahrenheit scales give the identical numeric value. This occurs because the linear relationship °F = (°C × 9/5) + 32 equals °C when °C = −40. Solving for the intersection: °F = °C → °C = (°C × 9/5) + 32 → °C − (°C × 9/5) = 32 → −(4/5)°C = 32 → °C = −40. This is a useful fact for quick mental conversions when dealing with extreme cold temperatures.
Common oven temperature equivalents: 140 °C = 275 °F (very low), 160 °C = 325 °F (low), 180 °C = 350 °F (moderate), 200 °C = 400 °F (hot), 220 °C = 425 °F (very hot), 240 °C = 475 °F (maximum for most domestic ovens). Use this converter for exact conversions when following recipes from different countries. The conversion formula is °F = (°C × 9/5) + 32. For gas mark ovens (common in the UK), gas mark 4 equals 180 °C (350 °F).
Temperature measures the average kinetic energy of particles in a substance and indicates the direction of energy flow. Heat is thermal energy transferred between systems due to a temperature difference. A large object at a moderate temperature contains more thermal energy than a small object at a high temperature. For example, a swimming pool at 25 °C contains vastly more thermal energy than a hot cup of coffee at 80 °C. Temperature and heat are related through the specific heat capacity of the substance: Q = mcΔT, where Q is heat energy, m is mass, c is specific heat capacity, and ΔT is the temperature change. This converter handles temperature units only; for energy conversions, use the Energy Converter.
The required precision depends entirely on the application. Weather forecasts need only integer precision: 22 °C (72 °F) is sufficient for deciding how to dress. Cooking typically needs 5–10 degree Fahrenheit or 2–5 degree Celsius precision. Medical thermometers require 0.1 °C or 0.2 °F precision. Laboratory measurements may need 0.01 °C or better, especially near phase transitions. This converter displays two decimal places, which covers weather, cooking, medical, and most routine laboratory applications. For higher precision, the formulas are exact; the display is the limiting factor.
Comfortable room temperature is typically 20–22 °C (68–72 °F, 293–295 K). The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends 21–23 °C (70–74 °F) for occupied indoor spaces. Standard room temperature for scientific purposes is often defined as 20 °C (68 °F, 293.15 K) or 25 °C (77 °F, 298.15 K) depending on the field and standard.
The ideal gas law PV = nRT requires absolute temperature in Kelvin. Using Celsius or Fahrenheit directly produces incorrect results because the relationship between pressure, volume, and temperature is proportional only when measured from absolute zero. For example, doubling the temperature of a gas from 27 °C to 54 °C does not double the pressure at constant volume. Converting to Kelvin: 27 °C = 300.15 K and 54 °C = 327.15 K. The actual pressure ratio is 327.15 / 300.15 = 1.09, not 2. Always convert to Kelvin before using any thermodynamic equation that involves temperature as a variable.
Kelvin is the standard for all thermodynamic calculations, gas law applications, and any equation where temperature appears as an absolute variable. Celsius is used for reporting measured temperatures in most scientific publications and for everyday laboratory measurements. Fahrenheit is rarely used in research except in some fields within the United States, such as food science and certain areas of biomedical research. The International Temperature Scale of 1990 (ITS-90) defines practical temperature standards from 0.65 K to approximately 1,358 K and is the basis for all modern temperature calibration, expressed in both Celsius and Kelvin.
Yes. A 0.5 °C error in body temperature measurement can change a diagnosis: 37.5 °C (99.5 °F) is normal while 38.0 °C (100.4 °F) indicates fever. Vaccine cold chain monitoring requires knowing exact thresholds: 2 °C (35.6 °F) and 8 °C (46.4 °F) define the acceptable range. An incorrectly converted Fahrenheit reading of 47 °F (8.3 °C instead of the correct 46.4 °F) could falsely indicate a temperature excursion. Always use a reliable converter for clinical temperature conversions and double-check against known reference points.
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