How to convert a temperature
- Type the temperature you want to convert.
- Pick the scale it uses.
- Press Convert or watch the live result.
- Read the value in all four scales.
- Copy the results you need.
What this temperature converter gives you
- Fahrenheit and Celsius side by side with Kelvin and Rankine.
- A clear error for values below absolute zero.
- Notes for landmark points like freezing and boiling.
- Any of the four scales as the starting point.
- The distance above absolute zero.
- Live results with nothing sent anywhere.
Why temperature conversion needs an offset
Meters to feet is a simple multiply. Both scales start at zero for no length. Temperature scales do not share a zero point.
Celsius puts zero where water freezes. Fahrenheit puts zero at the freezing point of a salt water mix. Kelvin puts zero at absolute zero. So you must shift as well as scale. To go from Celsius to Fahrenheit you multiply by 9/5. Then you add 32.
The wrong order or a missing offset gives answers that look fine at some temperatures. At others they are badly wrong. A temperature converter removes that risk.
The one point where the scales meet
At −40 degrees Celsius and Fahrenheit show the same number. It is the only point where the two scales cross. That makes it a handy check. Does −40 fail to return −40? Then the math is wrong.
A quick mental shortcut helps for daily life. To go from Celsius to Fahrenheit double it and add 30. So 20 °C becomes about 70 °F. The exact answer is 68. The shortcut drifts at extremes. It works fine when you pick a jacket.
Common temperatures to know
| Point | Fahrenheit | Celsius |
|---|---|---|
| Water freezes | 32 °F | 0 °C |
| Cool room | 68 °F | 20 °C |
| Normal body temperature | About 98.6 °F | About 37 °C |
| Safe cooked chicken | 165 °F | 74 °C |
| Water boils at sea level | 212 °F | 100 °C |
| Common oven setting | 350 °F | About 177 °C |
Water boils at a lower temperature at high altitude. Food then takes longer to cook. Denver cooks know this well.
Kelvin and absolute zero
Kelvin starts at absolute zero. At that point particles have the least motion possible. It equals −273.15 °C. No object can get colder. Kelvin uses the same step size as Celsius. So you just add or subtract 273.15.
Kelvin starts at a true zero. So it is the only scale here where ratios mean something. 200 K really is twice as hot as 100 K in a physical sense. A claim that 20 °C is twice as hot as 10 °C means nothing. Its zero point was a choice.
Kelvin has no degree sign. Write 300 K and not 300 °K. It measures from a true zero and not from a reference point.
Rankine and where it survives
Rankine also starts at absolute zero. It uses Fahrenheit sized degrees. Water freezes at 491.67 °R. Engineers who work in Fahrenheit use it for heat and energy math that needs an absolute scale. It turns up in some American engineering work. Most people never meet it.
A quick temperature converter example
A European recipe says to bake at 180 °C. Enter 180 and pick Celsius. The tool shows 356 °F. Most US ovens step in 25 degree marks. So set the oven to 350 °F and check the food a little early.
Why the US uses Fahrenheit
Daniel Fahrenheit built his scale in the early 1700s. Britain and its colonies adopted it. Most countries later moved to Celsius with the metric system. The United States kept Fahrenheit for weather, cooking and home thermostats. A few other places such as the Bahamas and the Cayman Islands use it too.
Fans of Fahrenheit like its finer steps for air temperature. One Fahrenheit degree is smaller than one Celsius degree. So a forecast can show small changes without decimals. Science labs in the US still use Celsius and Kelvin.
Who uses a temperature converter?
Cooks follow foreign recipes. Travelers read weather reports abroad. Students solve science problems. Nurses and parents read thermometers in another scale. Engineers switch between metric and US units.
Your numbers stay private
The tool runs in your browser and sends nothing. Need other units? Use the unit converter. Want body weight in kilograms? Try the weight converter. Need distance units? The length converter helps.