Convert Celsius to Fahrenheit and Back, Instantly
This temperature converter turns any value into Celsius, Fahrenheit, Kelvin, Rankine, and Gas Mark at the same time. Type one number, pick its scale, and every other reading updates as you type — no formulas to memorize and no buttons to hunt for.
It is built for travelers reading a foreign forecast, cooks adapting an oven recipe, students learning physics, and engineers working in Kelvin or Rankine. Adjust the decimal precision, hide the scales you do not need, and copy any result with one click.
How to Convert a Temperature
Enter your value
Type the temperature you want to convert. Whole numbers (100), decimals (36.6), and negatives (-40) all work.
Pick the source scale
Open the unit dropdown to choose Celsius, Fahrenheit, Kelvin, Rankine, or Gas Mark. Use the built-in search box to jump straight to a scale, or tap Swap units to flip the two sides.
Read every result at once
The converted values appear instantly below, each with its symbol and full name. Your source scale is highlighted so it is easy to spot.
Fine-tune and copy
Set Decimals to 2, 4, 6, 8, or Auto, use Customize Units to show only the scales you need, then copy any single value or grab them all with Copy All Results.
Features
Multi-Scale Conversion
Enter one value and see Celsius, Fahrenheit, Kelvin, Rankine, and Gas Mark side by side, with no extra calculations.
Precise Calculations
Conversions use the exact formulas, such as °F = (°C × 9/5) + 32 and K = °C + 273.15, for accurate results every time.
Gas Mark Support
Includes the UK and Irish oven Gas Mark scale, from ¼ to 10, shown with clean fraction values for cooking.
Swap & Searchable Units
Flip the two scales with one tap, or filter the unit list as you type to find the scale you want instantly.
Customizable Display
Toggle individual scales on or off so your results show only the conversions you actually care about.
Adjustable Precision
Choose 2, 4, 6, or 8 decimal places, or use Auto to drop trailing zeros — handy for both kitchens and labs.
One-Click Copying
Copy any single result, or use Copy All Results to grab every conversion at once for documents and notes.
Unit Reference Panel
Expand the reference to see where each scale is used, the core conversion formulas, and key freeze and boil points.
Works on Any Device
The layout adapts to desktop, tablet, and phone, and runs offline in your browser after the first load.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8), then add 32: °F = (°C × 9/5) + 32. For example, 20°C becomes (20 × 1.8) + 32 = 68°F. In the converter you just type the number and pick Celsius — the Fahrenheit result appears instantly.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9: °C = (°F − 32) × 5/9. For example, 98.6°F becomes (98.6 − 32) × 5/9 = 37°C. Select Fahrenheit as the source scale and the Celsius value is calculated for you.
How do I convert Celsius to Kelvin?
Add 273.15 to the Celsius value: K = °C + 273.15. So 0°C equals 273.15 K and 100°C equals 373.15 K. One Kelvin degree is the same size as one Celsius degree, so only the starting point shifts.
Is there a quick way to estimate Celsius to Fahrenheit?
For a rough number, double the Celsius value and add 30 (20°C ≈ 70°F). It is close enough for weather but not exact, since the real factor is 1.8 rather than 2. When you need the precise answer, the converter does the exact math for you.
At what temperature are Celsius and Fahrenheit equal?
They meet at -40 degrees: -40°C is exactly -40°F. It is the only point where both scales show the same number.
What is absolute zero?
Absolute zero is the lowest possible temperature, where molecular motion theoretically stops. It equals 0 Kelvin, -273.15°C, or -459.67°F. Because Kelvin and Rankine start from this point, they never go negative.
What is Gas Mark and where is it used?
Gas Mark is an oven temperature scale used mainly in the United Kingdom and Ireland, running from ¼ to 10. Each step is about a 14°C increase, so Gas Mark 1 is roughly 135°C (275°F) and higher marks reach about 260°C. The converter shows Gas Mark in familiar fraction values.
What is the Rankine scale?
Rankine is an absolute scale like Kelvin, but it uses Fahrenheit-sized degrees. It starts at absolute zero, where 0°R equals -459.67°F. It shows up in some engineering work, particularly in the United States.
Can I convert negative temperatures?
Yes. Just type a minus sign before the number, such as -10. The converter handles negative values correctly across every scale.
Do I need an internet connection to use this tool?
Only for the first load. After that, every calculation runs in your browser, so the converter keeps working offline and nothing you enter is sent to a server.
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