Temperature Converter
Convert between Celsius, Fahrenheit and Kelvin instantly, using exact formulas.
Conversions use exact standard formulas. For medical, scientific or safety-critical readings, confirm with a calibrated instrument rather than relying on a manual conversion.
How it works
Enter a value
Negative numbers are fine — temperatures often are.
Pick your two scales
Choose "From" and "To" among Celsius, Fahrenheit and Kelvin, or hit swap to flip them.
Read the result
The converted temperature updates instantly using the exact formula for that pair of scales.
What people use a temperature converter for
Temperature scales mix constantly depending on where a recipe, forecast or reading comes from.
Baking & recipes
Weather while traveling
School science projects
Thermostats & equipment
Body temperature readings
A few things worth knowing about temperature scales
The three scales this tool covers are used for different reasons. Celsius is the everyday standard across most of the world, built around water: 0°C is freezing, 100°C is boiling at sea level. Fahrenheit is still the everyday scale in the United States, with a finer-grained spacing between degrees that many people who grew up with it find more intuitive for describing weather and body temperature. Kelvin belongs to science — it uses the same size "step" as Celsius, but starts counting from absolute zero instead of from water's freezing point, which makes it the natural choice for physics and chemistry where negative temperatures would be awkward to work with.
Absolute zero, 0 K, is the reason Kelvin never goes negative: it's the coldest temperature that's physically possible, the point at which particles have essentially no thermal energy left to lose. That's not an arbitrary starting line the way 0°C or 0°F are — it's a real physical limit, which is why this converter treats a negative Kelvin value as invalid rather than just an unusual number.
For everyday mental math, two reference points cover most situations: 0°C is 32°F, and 100°C is 212°F. Knowing those two anchors makes it easy to sanity-check a conversion at a glance — if a "72°F" result doesn't feel roughly like a mild room temperature, or a "35°C" doesn't feel like a genuinely hot day, something in the input was probably off.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32: F = (C × 9/5) + 32. Pick Celsius as "From" and Fahrenheit as "To" and this calculator applies that formula instantly.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit value, then multiply by 5/9: C = (F − 32) × 5/9.
What is Kelvin and why can't it go below zero?
Kelvin is the scientific temperature scale where 0 K is absolute zero — the coldest temperature physically possible, the point where particles have the minimum possible thermal energy. Because nothing can be colder than that, negative Kelvin values aren't physically meaningful, so this calculator blocks them.
What are some easy reference points to remember?
Water freezes at 0°C / 32°F and boils at 100°C / 212°F (at sea-level pressure). Those two anchors are enough to sanity-check most everyday conversions without needing a calculator.
Which scale is used where?
Celsius is the everyday standard in most of the world. Fahrenheit is still the everyday standard in the United States. Kelvin is the standard in scientific work, since it starts at absolute zero and has no negative values.
Is this temperature converter free to use?
Yes, completely free, with no account or sign-up, and it runs entirely in your browser.