Temperature converter

Convert a reading in three steps

Enter the temperature as a number, choose the scale used by the source, and choose the scale you need. Select Convert temperature to update the result. The Swap units button exchanges the two scales and places the last result back into the input, which is useful for a quick reverse check.

The input accepts positive values, zero, and negative values where the selected scale permits them. Type a decimal point rather than a comma and leave symbols such as °C, °F, and K out of the field. The result can be copied as a plain number with its unit, ready to paste into a note or worksheet.

How the conversion works

Celsius and Kelvin use equal-sized intervals but different zero points: K = °C + 273.15 and °C = K − 273.15. Fahrenheit uses a different interval and offset: °F = °C × 9/5 + 32, while °C = (°F − 32) × 5/9. The converter first maps the source value to Kelvin and then maps Kelvin to the requested scale, keeping full JavaScript numeric precision until display.

Kelvin is written K, without a degree sign. Absolute zero is 0 K, −273.15 °C, or −459.67 °F. The tool checks the starting value against that boundary. It does not silently replace an impossible temperature with zero, because doing so would change the user’s measurement.

Worked examples

Example 1: enter 20, select Celsius, and convert to Fahrenheit. The calculation is 20 × 9/5 + 32, so the displayed result is 68 °F. Swapping the units and converting 68 °F returns 20 °C.

Example 2: enter 300, select Kelvin, and convert to Celsius. Subtracting 273.15 gives 26.85 °C. A boundary example is 0 K, which converts to −273.15 °C and −459.67 °F. By contrast, −1 K is rejected because it lies below absolute zero.

When to use it—and what it does not decide

The converter is suitable for weather readings, laboratory notes, appliance specifications, and international documents when the source uses one of the three supported scales. It converts the numeric scale only. It does not assess fever, food safety, oven settings, laboratory safety, sensor calibration, or measurement uncertainty, and it gives no medical or cooking recommendation.

This page handles absolute temperatures. Temperature differences follow different rules because offsets cancel: a change of 1 °C equals a change of 1 K and a change of 1.8 °F. Do not use an absolute conversion result as a converted temperature difference. Very small nonzero results use significant digits so they are not displayed as zero; ordinary results show no more than two decimal places.

Input and result limits

Scientific notation, grouped numbers, units, and expressions are not accepted. Enter 1000 rather than 1,000, and enter the already evaluated value rather than 20+5. Inputs are limited to an absolute value of one trillion to keep display and copy output practical. Editing the value clears the result until you select Convert temperature; after a conversion, changing either unit updates the result immediately without another confirmation.

The copied number uses a decimal point and no grouping regardless of the page language. Display formatting follows the selected page language and may use a local decimal separator. No input is stored, uploaded, or included in analytics by this page.

Conversion formulas and examples

Choose the source and target temperature scales above. These examples convert a temperature reading, not a temperature change. Enter numbers without °C, °F or K.

Why does 20 °C become 68 °F?

Fahrenheit has a different zero point and interval size. Multiplying 20 by 9/5 and adding 32 gives 68.

Can Kelvin be negative?

Not for an absolute thermodynamic temperature. This converter rejects values below 0 K and the equivalent limits in Celsius and Fahrenheit.

Why is Kelvin shown without a degree symbol?

The SI unit name and symbol are kelvin and K. Unlike Celsius and Fahrenheit, its symbol does not use the degree sign.

Does this convert a temperature change?

No. It converts a point on a temperature scale. For differences, 1 °C equals 1 K, while 1 °C equals 1.8 °F.

Why might my result have fewer decimals?

Ordinary results are rounded to at most two decimal places and trailing zeros are removed. The calculation retains precision before that final display step.