About the Temperature Converter
Celsius is used for weather and cooking in most of the world, Fahrenheit is used in the United States, and Kelvin is the scientific scale that starts at absolute zero. Unlike length or weight, temperature scales do not share a zero point, so you cannot convert them by simply multiplying. This converter applies the correct formulas and warns you if a value is below absolute zero, which is physically impossible.
How to use the Temperature Converter
- Enter a temperature. Negative values are allowed.
- Choose the scale you are converting from and to.
- Read the result; the table shows the value on all three scales.
The formula behind it
Reference temperatures
Some useful anchors:
- Water freezes: 0 °C = 32 °F = 273.15 K.
- Average body temperature: about 37 °C = 98.6 °F.
- Water boils (at sea level): 100 °C = 212 °F.
- Moderate oven: 180 °C ≈ 356 °F (recipes often round to 350 °F).
- Celsius and Fahrenheit are equal at −40°.
A quick mental shortcut
To estimate °F from °C, double the Celsius figure and add 30. For 20 °C this gives 70 °F (the exact answer is 68 °F). It works best for everyday weather temperatures and becomes less accurate at extremes.
Examples
Weather
25 °C × 9/5 + 32 = 77 °F.
Fever check
101 °F: (101 − 32) × 5/9 = 38.3 °C.
Frequently asked questions
What is the formula for Celsius to Fahrenheit?
Multiply by 9/5 (or 1.8) and add 32. So 30 °C = 30 × 1.8 + 32 = 86 °F.
Why is Kelvin written without a degree sign?
Kelvin is an absolute scale defined by the International System of Units, so its unit is simply the kelvin (K), not a degree.
What is absolute zero?
0 K, which is −273.15 °C or −459.67 °F. Nothing can be colder.
Sources
About the author: Ahmed Bilal
Ahmed Bilal is the founder of VolexTool and builds and maintains every calculator on the site. Tax rates and thresholds are taken directly from official sources such as GOV.UK, HMRC, the Canada Revenue Agency and the Australian Taxation Office, the formula is shown on every page, and each update must pass more than 600 automated checks before it goes live. Ahmed is not a tax adviser: for decisions about your own situation, speak to a qualified accountant or financial adviser.