Temperature Converter
A temperature converter turns one reading into the other scales. Enter a number, pick its scale, and all four appear at once to two decimals: 20 °C is 68.00 °F, 293.15 K and 527.67 °R. The Fahrenheit formula is °F = °C × 9/5 + 32, so 100 °C gives 212.00 °F and −40 °C gives −40.00 °F, the one point where the two scales agree.
Method and limits
Enter a complete number; dot decimals are accepted. A decimal comma also works in comma-decimal locales. Blank is unavailable, not zero. No grouping or unit suffixes. Maximum 100 significant digits, exponent −100…100, 256 characters. Display uses two decimal places, with trailing zeros removed and halfway cases rounded away from zero; tiny nonzero values use scientific notation. Calculations run in your browser; surrounding site requests still exist.
Below absolute zero (-273.15 °C / -459.67 °F / 0 K)
Conversion Formulas
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About Temperature Converter
Convert Celsius, Fahrenheit, Kelvin and Rankine with an absolute-zero warning. °F = °C × 9/5 + 32; K = °C + 273.15; °R = K × 9/5. K < 0: ⚠.
0 °C → 32 °F / 273.15 K / 491.67 °R; −40 °C → −40 °F.
Illustrative examples; no publication or accuracy certification.
Use Cases
How to use
Choose units, enter a number, then read or copy the current result.
Pro Tips
- Display uses two decimal places, with trailing zeros removed and halfway cases rounded away from zero; tiny nonzero values use scientific notation.
Troubleshooting
Every card shows a conversion of zero even though the field looks empty.
An empty or unreadable input is treated as 0, so the cards fall back to 0 °C, 32.00 °F, 273.15 K and 491.67 °R. That is the tool's default, not a stuck value — type a figure into Temperature and all four update immediately.
The results are dimmed and there is a red line under the input.
That is the below-absolute-zero warning: your value converts to colder than −273.15 °C. Most often the Scale dropdown is on the wrong scale — 200 entered as Celsius is fine, but −300 is not, and a Kelvin figure entered as Rankine can fall below the limit too.
A preset button changed my scale as well as the number.
The presets are defined in Celsius, so loading one sets both the value and the Scale dropdown to Celsius. The label on each button shows this — body temperature reads 37 °C. Change the dropdown afterwards if you wanted the same figure read as another scale.
The thermometer bar does not move when I change the temperature.
The bar covers −40 °C to 100 °C only. Anything colder sits empty at the bottom and anything hotter fills it completely, so a jump from 150 °C to 400 °C leaves it looking identical. The numbers in the cards are the accurate readout.
Copy did not put anything on my clipboard.
Copying uses the browser clipboard API, which needs a secure page and a real click and can be blocked by an extension. If the button does not switch to its tick, select the four numbers in the cards and press Ctrl+C, or Cmd+C on a Mac.
Frequently Asked Questions
Multiply Celsius by 9/5 and add 32 to obtain Fahrenheit. Thus 0 °C = 32 °F and −40 °C = −40 °F. The calculation uses exact rational arithmetic before display rounding.
A negative Kelvin value is below absolute zero. Arithmetic conversions remain visible with a warning; they are not physically valid measurements.