Unit conversion calculator
Temperature Converter
Convert Celsius, Fahrenheit and Kelvin for weather, cooking, science and equipment settings without using a simple ratio incorrectly.
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How the temperature converter works
Temperature scales do not all begin at the same zero point, so conversion needs both a scale factor and an offset. The calculator converts the entered value to Celsius, then converts Celsius to the selected output scale. It also rejects Kelvin values below absolute zero.
| Conversion | Formula | Reference point |
|---|---|---|
| °C to °F | °F = (°C × 9/5) + 32 | 0°C = 32°F |
| °F to °C | °C = (°F − 32) × 5/9 | 212°F = 100°C |
| °C to K | K = °C + 273.15 | 0°C = 273.15 K |
| K to °C | °C = K − 273.15 | 0 K = −273.15°C |
For 20°C, multiplying by 9/5 gives 36, then adding 32 gives 68°F. A shortcut that multiplies by 1.8 but forgets the 32-degree offset will be wrong except at special points.
Absolute temperatures and temperature differences
Celsius and Fahrenheit are commonly used for weather, rooms, cooking and equipment. Kelvin is an absolute thermodynamic scale used in scientific work and is written without a degree symbol.
Converting a temperature difference is not the same as converting an actual temperature. An increase of 10°C equals an increase of 18°F because only the scale factor applies; you do not add 32 to a difference. The Kelvin interval is the same size as the Celsius interval, so a change of 10 K equals a change of 10°C.
Negative Celsius and Fahrenheit values are valid. Negative Kelvin values are not valid on the ordinary thermodynamic scale, which is why the calculator displays a warning below 0 K.
Worked temperature conversion examples
Weather: 35°C to Fahrenheit
35°C equals 95°F. This is a hot-weather comparison, but “feels like” values can differ because humidity, wind and exposure are separate factors.
Oven setting: 350°F to Celsius
350°F converts to about 176.667°C, commonly rounded to 175°C or 180°C depending on the oven and recipe. Fan-forced adjustments are a cooking instruction, not part of the temperature-unit conversion.
Body temperature: 37°C to Fahrenheit
37°C equals 98.6°F. A converted reading does not determine whether a measurement method, device or clinical interpretation is appropriate.
Scientific reference: 300 K to Celsius
300 kelvin equals 26.85°C. The number of kelvins is not written with a degree symbol.
Temperature conversion mistakes
- Using only multiplication: Celsius and Fahrenheit require the 32-degree offset as well as the 9/5 scale factor.
- Adding 32 to a temperature change: offsets apply to absolute readings, not differences.
- Writing “degrees Kelvin”: the unit is kelvin, symbol K.
- Converting an oven instruction without fan context: conventional and fan-forced settings are not merely different units.
- Treating a converted reading as a diagnosis or calibration: device accuracy and interpretation remain separate.
Useful checkpoints are −40°C = −40°F, 0°C = 32°F and 100°C = 212°F at standard reference conditions. A result far from these relationships deserves a formula check.
Rounding, sensors and practical use
Weather displays usually need whole degrees. Cooking often uses the nearest 5°C or 10°F because domestic ovens cycle around their setting. Laboratory and equipment work may require calibrated sensors, uncertainty records and more decimal places.
The converter changes the unit only. It cannot account for thermometer placement, response time, infrared emissivity, altitude effects on boiling, oven hot spots or medical device instructions.
Temperature context matters as much as the converted number
Weather temperature, oven settings, body temperature and laboratory measurements all use the same scales but have different practical tolerances. A forecast of 25°C does not mean every location will be exactly 77°F; weather observations are rounded and conditions vary over distance and time. For travel, the converted value is best treated as an interpretation aid rather than a more precise forecast.
Oven dials can differ from the actual air temperature, and fan-forced settings may be lower than conventional-oven settings for the same recipe. Converting 180°C to 356°F handles the scale only. It does not apply a fan adjustment, account for hot spots or correct an uncalibrated thermostat. Follow the recipe’s oven type and use an oven thermometer when temperature accuracy matters.
Body and scientific temperatures
Body temperature depends on measurement site, device, technique, age and time of day. Converting a reading between Celsius and Fahrenheit does not determine whether it is clinically significant. Follow the device instructions and current health guidance, particularly for infants, vulnerable people or severe symptoms. This calculator is not a diagnostic tool.
Kelvin is an absolute thermodynamic scale and does not use the degree symbol. A change of one kelvin is the same size as a change of one degree Celsius, but the zero points differ by 273.15. Negative Kelvin values are not valid in the ordinary thermodynamic scale. Temperature differences also need careful wording: an increase of 10°C equals an increase of 18°F, even though converting the standalone value 10°C gives 50°F.
For refrigeration, industrial processes and scientific work, record sensor accuracy, calibration, measurement location and acceptable range. A formula can convert the display but cannot correct sensor lag, probe placement or equipment variation. Keep the unrounded converted value for intermediate calculations and round the final result to match the original instrument’s resolution.
Sanity checks across temperature scales
Several reference points make errors easier to spot: water freezes at 0°C or 32°F under standard conditions, ordinary room temperature is roughly in the low twenties Celsius or low seventies Fahrenheit, and water boils near 100°C or 212°F at standard atmospheric pressure. Boiling temperature changes with altitude and pressure, so it is a reference rather than a universal calibration test.
Because the scales have different zero points, multiplying alone is not enough. A result that maps 0°C to 0°F is wrong. For Kelvin, add 273.15 to Celsius; do not use a degree symbol and do not enter a value below absolute zero.
When recording controlled temperatures, include the sensor location and acceptable range. Air, surface, product core and liquid temperatures can differ substantially. The unit conversion should be applied to the actual measured quantity, not used to bridge readings taken at different locations or times.
For a conversion that will be reused in a procedure, record the formula, source scale and rounding rule rather than copying a single result without context. Automatic systems should also validate inputs: Kelvin cannot be negative, and an empty or non-numeric reading should not silently become zero. These controls matter more than displaying extra decimal places.
Where a threshold matters, compare the unrounded value with the threshold before formatting the display. Rounding 37.95°C to 38.0°C may be convenient, but the decision rule should specify whether it uses the measured reading, a rounded value or a stated range.
Temperature converter FAQs
Why do Celsius and Fahrenheit need an offset?
The scales use different zero points as well as different interval sizes, so multiplying alone cannot align them.
At what temperature are Celsius and Fahrenheit equal?
They are equal at −40, so −40°C is the same temperature as −40°F.
Can Kelvin be negative?
Not on the ordinary thermodynamic scale used by this calculator. Zero kelvin is absolute zero.
Is 180°C always the same oven setting as 350°F?
350°F is about 176.7°C, often rounded in recipes. Fan-forced or convection adjustments are separate from the unit conversion.
How do I convert a 5°C temperature rise to Fahrenheit?
For a difference, multiply by 9/5 without adding 32. A rise of 5°C equals a rise of 9°F.
Editorial review completed 2026-07-23: Temperature Converter formulas, unit labels, examples, regional assumptions, rounding guidance and calculator output were checked together. See the unit-conversion methodology and editorial review profile.