Temperature Converter and Visualizer

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   What’s great about our Temperature Converter and Visualizer

   For both kids and professionals to visualize temperatures

   • Free
   • Converts Celsius, Fahrenheit, Kelvin, Rankine and four historical scales instantly
   • Optional background animation: snowy mountains, falling snow, boiling water, fire and the Sun as you move the slider
   • No sign-up
   • No ads
   • Works offline once loaded
   • No daily limit
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   Choose which units to show

   Use the unit names at the top to show or hide each card. Drag a name or a card’s title to rearrange them; your order is remembered in this browser, and Restore puts the original order back. The four historical scales (Réaumur, Rømer, Newton and Delisle) are shown too.

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   Drag a slider or type a value

   Move any slider, or type a number into its “Type Value” box, and every visible unit updates instantly. With “Animation” on (it is on by default), watch snowy mountains appear when it is cold, then water boil, then fire and the Sun appear in the background as you move the slider.

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   Switch to higher temperatures

   Turn on “Higher Temps” to widen every slider’s range for extreme values.

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What is Temperature?

Temperature is how hot or cold something is. It measures the average energy of the tiny particles in a material: the faster they move, the higher the temperature. Most of the world uses Celsius, the United States uses Fahrenheit, and science uses Kelvin, which starts at absolute zero. This converter shows the same temperature on all of them, plus some historical scales.

About Celsius (°C)

Celsius is the temperature scale used by most of the world for everyday things like weather, cooking and school science. It was proposed in 1742 by Swedish astronomer Anders Celsius, and it’s built around water: 0°C is where water freezes, and 100°C is where it boils, both measured at normal air pressure.

• Part of the metric system, so it’s the default scale almost everywhere except the United States
• Easy to convert to Kelvin: just add 273.15 (0°C = 273.15K)
• To convert to Fahrenheit: multiply by 9/5, then add 32
• Common reference points: 20°C is a mild room temperature, 37°C is normal human body temperature

About Fahrenheit (°F)

Fahrenheit is the temperature scale used mainly in the United States, along with a few other countries and territories. It was created in 1724 by physicist Daniel Gabriel Fahrenheit, who based his scale on a mix of brine’s freezing point and average human body temperature. On this scale, water freezes at 32°F and boils at 212°F.

• Used day-to-day for weather forecasts and cooking in the US
• Has a 180-degree gap between freezing and boiling, giving finer detail for everyday temperature changes
• To convert to Celsius: subtract 32, then multiply by 5/9
• Common reference points: 68°F is a comfortable room temperature, 98.6°F is normal human body temperature

About Kelvin (K)

Kelvin is the official SI (scientific) unit of temperature, used by scientists and engineers worldwide in fields like physics, chemistry and astronomy. It’s named after Lord Kelvin (William Thomson), and unlike Celsius or Fahrenheit, it has no negative numbers — it starts at absolute zero, the coldest temperature theoretically possible, where molecules stop moving entirely.

• Absolute zero is 0K, equal to −273.15°C — nothing can be colder
• Kelvin doesn’t use a degree symbol; it’s written as “300K”, not “300°K”
• Each Kelvin step is the same size as a Celsius step, so K = °C + 273.15
• Water freezes at 273.15K and boils at 373.15K

About Rankine (°R)

Rankine is an absolute temperature scale mainly used in US engineering fields such as aerospace and thermodynamics. It was named after Scottish engineer William John Macquorn Rankine. Like Kelvin, it starts at absolute zero with no negative values, but its degree size matches Fahrenheit rather than Celsius, which makes it convenient for engineers already working in Fahrenheit.

• Absolute zero is 0°R, exactly equal to 0K and −273.15°C
• Each Rankine degree is the same size as a Fahrenheit degree, so °R = °F + 459.67
• Mostly used in specialized engineering and thermodynamics work, rarely in everyday life
• Water freezes at 491.67°R and boils at 671.67°R

About Réaumur (°Ré)

Réaumur is an old temperature scale created in 1730 by French scientist René Antoine Ferchault de Réaumur. It was once widely used across Europe, especially in France, Germany and Russia, and it divides the gap between freezing and boiling water into 80 equal degrees instead of 100.

• Water freezes at 0°Ré and boils at 80°Ré
• To convert to Celsius: multiply by 5/4. To convert to Fahrenheit: multiply by 9/4, then add 32
• Absolute zero is −218.52°Ré, equal to 0K and −273.15°C
• Rarely used today, mostly found in historical texts and a few traditional trades such as cheese-making

About Rømer (°Rø)

Rømer is one of the earliest standardized temperature scales, created around 1701 by Danish astronomer Ole Rømer. It is set so that water freezes at 7.5°Rø and boils at 60°Rø. It matters historically because Daniel Gabriel Fahrenheit met Rømer and built his own scale on this work.

• Each Rømer degree equals 40/21 of a Celsius degree, about 1.9°C
• To convert to Celsius: subtract 7.5, then multiply by 40/21
• Absolute zero is −135.90°Rø, equal to 0K and −273.15°C
• No longer used, but it is an important step between the first thermometers and Fahrenheit

About Newton (°N)

The Newton scale was described by Isaac Newton in a 1701 paper on measuring heat. It is set so that water freezes at 0°N and boils at 33°N. It has nothing to do with the newton, the unit of force.

• Each Newton degree equals 100/33 of a Celsius degree, about 3.03°C
• To convert to Celsius: multiply by 100/33
• Absolute zero is −90.14°N, equal to 0K and −273.15°C
• Never widely adopted, and today it is mostly of historical interest

About Delisle (°De)

The Delisle scale was created in 1732 by French astronomer Joseph-Nicolas Delisle, who used it while working in Russia, where it stayed in use for about a century. It runs backwards: water boils at 0°De and freezes at 150°De, so hotter temperatures have lower numbers.

• Every Delisle degree equals 2/3 of a Celsius degree, counted downwards from the boiling point
• To convert to Celsius: subtract the Delisle value multiplied by 2/3 from 100
• Temperatures above boiling water are negative, and absolute zero is 559.73°De
• On our Delisle slider, hot is on the left and cold is on the right, matching the backwards numbers

About Wedgwood and Leiden scales

Two more historical scales are not included as cards because they can’t be converted to modern temperatures reliably.

• Wedgwood (°W): created in 1782 by potter Josiah Wedgwood to measure kiln temperatures. It starts at 1,000°F (about 538°C), and each degree equals 130°F. Its readings were based on how much clay shrank, so they are only rough estimates
• Leiden (°L): a low-temperature calibration scale from the early 1900s, used in the Leiden cryogenics laboratory below −183°C. It is set by fixed points, with hydrogen boiling (−253°C) at 0 and oxygen boiling (−183°C) at 70, so it is a lab convention rather than a true conversion formula