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Temperature Converter

Convert between Celsius, Fahrenheit, and Kelvin temperature scales instantly.

Temperature Reference

Description°C°FK
Absolute Zero-273.15-459.670
Freezing Point of Water032273.15
Room Temperature20-2568-77293-298
Body Temperature3798.6310.15
Boiling Point of Water100212373.15

Related Calculators

Celsius to Fahrenheit ConverterFahrenheit to Celsius ConverterCelsius to Kelvin ConverterKelvin to Celsius ConverterFahrenheit to Kelvin ConverterKelvin to Fahrenheit Converter

What is Temperature Converter?

A temperature converter is an essential tool for converting between the three major temperature scales used worldwide: Celsius (also called centigrade), Fahrenheit, and Kelvin. Temperature measurement has been fundamental to science, medicine, cooking, and everyday life since the invention of the first reliable thermometers in the early 18th century. The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in 1724, a German physicist working in the Netherlands. He originally set 0 degrees as the temperature of a brine solution (the coldest he could reliably reproduce in his laboratory) and 96 degrees as approximate human body temperature, later refined so that water freezes at 32 degrees F and boils at 212 degrees F.

The Celsius scale was created by Swedish astronomer Anders Celsius in 1742, originally with 0 as the boiling point and 100 as the freezing point of water (later inverted by Carl Linnaeus). This centigrade design, with exactly 100 degrees between the freezing and boiling points of water at standard atmospheric pressure, made it intuitive for scientific work and everyday use. The scale was renamed from centigrade to Celsius in 1948 to honor its creator and avoid confusion with the centesimal grade used in angular measurement. Today, Celsius is the standard temperature unit in virtually every country except the United States.

The Kelvin scale was proposed by Irish-Scottish physicist William Thomson (later Lord Kelvin) in 1848 as an absolute temperature scale for scientific use. It starts at absolute zero (0 K = -273.15 degrees C), the theoretical temperature at which all thermal molecular motion ceases. The Kelvin uses the same increment size as the Celsius degree but shifts the zero point to absolute zero, eliminating negative temperatures. It is the SI base unit of temperature and is required in scientific formulas involving gas laws, thermodynamics, Stefan-Boltzmann radiation law, and many other physics and chemistry equations. Our converter handles conversions between all three scales with precision.

How to Use This Calculator

Using the temperature converter is straightforward. Enter the temperature value in any one of the three scales (Celsius, Fahrenheit, or Kelvin) and the converter instantly displays the equivalent in the other two scales. You can enter negative values, decimals, and very large numbers for scientific applications. The conversion is bidirectional, so you can start with any scale as your input.

For everyday use, the most common conversions are between Celsius and Fahrenheit for weather and cooking. For scientific and engineering work, Celsius to Kelvin conversion is frequently needed. The converter handles all edge cases including absolute zero (-273.15 degrees C = -459.67 degrees F = 0 K), the freezing and boiling points of water, and extreme temperatures encountered in industrial and astronomical contexts.

Formula

Celsius to Fahrenheit: °F = (°C × 9/5) + 32
Fahrenheit to Celsius: °C = (°F - 32) × 5/9
Celsius to Kelvin: K = °C + 273.15
Kelvin to Celsius: °C = K - 273.15
Fahrenheit to Kelvin: K = (°F - 32) × 5/9 + 273.15
Kelvin to Fahrenheit: °F = (K - 273.15) × 9/5 + 32

Worked Examples

Body Temperature: Fever Check

A thermometer reads 101.3 degrees Fahrenheit. Converting to Celsius: (101.3 - 32) x 5/9 = 69.3 x 0.5556 = 38.5 degrees C. Since a fever is defined as above 38 degrees C (100.4 degrees F), this reading confirms a mild fever. In Kelvin, this is 311.65 K. Understanding temperature in multiple scales is important when consulting medical references from different countries.

Water Freezing and Boiling Points

Water freezes at 0 degrees C = 32 degrees F = 273.15 K, and boils at 100 degrees C = 212 degrees F = 373.15 K at standard atmospheric pressure (1 atm). These are the fundamental reference points of the Celsius scale. At higher altitudes, water boils at lower temperatures (approximately 95 degrees C or 203 degrees F in Denver, Colorado at 1,600 meters elevation) due to reduced atmospheric pressure.

Comfortable Room Temperature

The generally accepted comfortable room temperature is 20-22 degrees C, which equals 68-72 degrees F or 293-295 K. Most thermostats in the US are set in Fahrenheit (typically 68-72 degrees F), while European thermostats use Celsius (20-22 degrees C). When moving between countries or using imported climate control equipment, knowing this conversion ensures comfortable indoor environments.

Extreme Temperature Records

The highest recorded air temperature on Earth was 56.7 degrees C (134 degrees F) in Death Valley, California in 1913. The coldest was -89.2 degrees C (-128.6 degrees F) at Vostok Station in Antarctica in 1983. In Kelvin, these are 329.85 K and 184.0 K respectively. These extremes span a range of about 146 degrees C (263 degrees F), showcasing the remarkable temperature range found on our planet.

Common Temperature Reference Points

DescriptionCelsius (°C)Fahrenheit (°F)Kelvin (K)
Absolute Zero-273.15-459.670
Coldest Recorded on Earth-89.2-128.6184.0
Water Freezes032273.15
Refrigerator439.2277.15
Cool Day1050283.15
Room Temperature20-2268-72293-295
Warm Day3086303.15
Normal Body Temp3798.6310.15
Fever38+100.4+311.15+
Hottest Recorded on Earth56.7134329.85
Water Boils100212373.15
Oven (Baking)180350453.15
Oven (High)230450503.15
Wood Burns300572573.15

Countries Using Fahrenheit vs Celsius

Temperature ScaleCountries/RegionsNotes
FahrenheitUnited StatesWeather, cooking, daily life
FahrenheitUS territories (Guam, Puerto Rico, USVI)Following US convention
FahrenheitCayman Islands, BahamasDue to US influence
Fahrenheit (partial)United KingdomOlder generation; media sometimes uses both
CelsiusAll of Europe (except UK partial)EU standard since metrication
CelsiusAll of AsiaIncluding China, India, Japan
CelsiusAll of AfricaIncluding South Africa, Nigeria, Egypt
CelsiusAll of South AmericaIncluding Brazil, Argentina
CelsiusCanadaOfficial metric; some Fahrenheit usage near US border
CelsiusAustralia, New ZealandFully metric since 1970s

Cooking Temperature Guide

Cooking MethodCelsius (°C)Fahrenheit (°F)Gas Mark
Very Low / Warming1202501/2
Low / Slow Cook1503002
Moderate1603253
Moderate1803504
Moderately Hot1903755
Hot2004006
Hot2204257
Very Hot2304508
Very Hot2404759
Broil / Grill260+500+10

Benefits of Using This Calculator

  • Convert weather temperatures between Celsius and Fahrenheit for international travel
  • Translate cooking and oven temperatures between US (Fahrenheit) and international (Celsius) recipes
  • Check body temperature readings in the scale used by your healthcare provider
  • Convert scientific temperatures to and from Kelvin for physics and chemistry calculations
  • Understand industrial temperature specifications in different measurement systems
  • Set heating and cooling thermostats correctly when using equipment from different countries
  • Compare climate data and weather forecasts from international sources
  • Essential for HVAC, refrigeration, and food safety temperature compliance

Practical Tips

  • For a quick Celsius to Fahrenheit estimate, double the Celsius value and add 30. This gives answers within a few degrees for the 0-35 degree C range most relevant to weather.
  • Key anchors to memorize: 0 C = 32 F (freezing), 20 C = 68 F (room temp), 37 C = 98.6 F (body temp), 100 C = 212 F (boiling).
  • When precision matters (medical, scientific), always use the exact formula. The quick estimation tricks can be off by 2-4 degrees.
  • For oven temperatures, remember that 180 C = 350 F is the most common baking temperature. Add or subtract 10 C (approximately 20 F) for variations.
  • Kelvin is simply Celsius plus 273.15. There are no negative Kelvin values. If you get a negative Kelvin, you have made a calculation error.

Related Concepts

Absolute Zero

Absolute zero (0 K = -273.15 degrees C = -459.67 degrees F) is the lowest possible temperature, where all thermal molecular motion ceases. It has never been achieved in practice, though laboratories have reached within a fraction of a nanodegree. At absolute zero, a system is in its quantum ground state with minimal energy. The Third Law of Thermodynamics states that it is impossible to reach absolute zero through any finite number of cooling steps.

Rankine Scale

The Rankine scale is an absolute temperature scale based on Fahrenheit degree increments, starting at absolute zero (0 degrees R = -459.67 degrees F). It is related to Fahrenheit in the same way that Kelvin is related to Celsius. Rankine is used primarily in some American engineering applications, particularly in thermodynamics and heat transfer calculations in industries that traditionally use Fahrenheit. To convert: R = F + 459.67.

Thermodynamics Basics

Thermodynamics is the branch of physics dealing with heat, work, and temperature. The three laws describe how energy moves: the First Law (energy is conserved), the Second Law (entropy always increases in isolated systems), and the Third Law (entropy approaches zero as temperature approaches absolute zero). Temperature is a fundamental thermodynamic quantity that determines the direction of heat flow - heat always flows spontaneously from higher to lower temperature.

Heat Index

The heat index (also called the apparent temperature or feels-like temperature) combines air temperature and relative humidity to indicate how hot it actually feels to the human body. At 35 degrees C (95 degrees F) with 60% humidity, the heat index can be 45 degrees C (113 degrees F) or higher, representing dangerous conditions. The heat index is critical for weather safety warnings and outdoor activity planning.

Key Takeaways

  • 1The three main temperature scales are Celsius (used globally), Fahrenheit (used in the US), and Kelvin (used in science).
  • 2The conversion formulas are: F = (C x 9/5) + 32, C = (F - 32) x 5/9, and K = C + 273.15.
  • 3-40 degrees is the only temperature that reads the same on both Celsius and Fahrenheit scales.
  • 4Water freezes at 0 C / 32 F and boils at 100 C / 212 F - these are the fundamental reference points.
  • 5For quick estimation, double Celsius and add 30 to get approximate Fahrenheit (accurate for weather range temperatures).

Frequently Asked Questions

To convert Celsius to Fahrenheit, multiply the Celsius value by 9/5 (or 1.8) and add 32. The formula is: F = (C x 9/5) + 32. For example, 25 degrees Celsius equals (25 x 1.8) + 32 = 77 degrees Fahrenheit. A quick estimation trick is to double the Celsius value and add 30, which gives a rough approximation. For instance, 20 degrees C doubled is 40, plus 30 equals 70 degrees F (exact answer is 68 degrees F), which is close enough for everyday use.

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