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Calculator Answers

Temperature Converter

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A temperature converter is a measurement utility that translates thermal values between different temperature scales. The converter supports conversions across Celsius, Fahrenheit, Kelvin, and Rankine scales. It applies exact thermodynamic algebraic formulas, such as Celsius equals Fahrenheit minus thirty-two multiplied by five-ninths, and Kelvin equals Celsius plus two hundred seventy-three point fifteen, ensuring high accuracy. Students, scientists, chefs, and international travelers use this tool to standardize temperature measurements across different systems and regions.

Pick a 'from' scale, a 'to' scale, and enter a temperature. The calculator returns the converted value plus equivalents in every supported scale.

See also: Length Converter and Air Fryer Conversion Calculator.

Quick Answer

Convert temperatures between Celsius, Fahrenheit, Kelvin, and Rankine. Enter your temperature value and select your starting and target units for instant conversion results.

Negative values OK (e.g., -40 °C). Cannot be below absolute zero. · e.g. 100

Internal base unit is Kelvin. Absolute zero: 0 K = -273.15 °C = -459.67 °F = 0 °R.

Temperature

Celsius → Fahrenheit

212 °F

100 °C = 212 °F

Celsius (°C)100 °C
Fahrenheit (°F)212 °F
Kelvin (K)373.15 K
Rankine (°R)671.67 °R

C to F: × 9/5 + 32. F to C: (F − 32) × 5/9. C to K: + 273.15. F to R: + 459.67. Kelvin and Rankine are absolute scales (no negative values).

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Examples

100 °C to °F

= 212 °F

98.6 °F to °C

= 37 °C (body temperature)

0 K to °F

= -459.67 °F (absolute zero)

How it works

Temperature conversion uses both a scale factor and an offset. Internally, every input is converted to Kelvin first, then to the target scale. This keeps formulas consistent and rules out impossible values below absolute zero.

C to F · F = C × 9/5 + 32

F to C · C = (F − 32) × 5/9

C to K · K = C + 273.15

F to R · R = F + 459.67

Absolute zero: 0 K = -273.15 °C = -459.67 °F = 0 °R.

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Frequently asked questions

F = C × 9/5 + 32. So 0 °C = 32 °F (water freezes), 100 °C = 212 °F (water boils), 37 °C ≈ 98.6 °F (normal body temperature). The inverse is C = (F − 32) × 5/9.

Most unit conversions are pure scale (multiply by a factor). Temperature scales also have different zero points, so the conversion includes an offset. Celsius and Fahrenheit have arbitrary zero points; Kelvin and Rankine start at absolute zero.

The coldest theoretically possible temperature, where all motion of particles stops. It is 0 K = -273.15 °C = -459.67 °F = 0 °R. The calculator flags inputs below absolute zero in the chosen scale because they are not physically meaningful.

Kelvin is the SI base unit of temperature, used in science and engineering. It uses the same step size as Celsius (1 K change = 1 °C change), but starts at absolute zero instead of water's freezing point. Kelvin is always written without a degree symbol.

Rankine is the Fahrenheit-equivalent absolute scale: same step size as Fahrenheit (1 °R = 1 °F change), but starts at absolute zero. Common in engineering contexts that historically used Fahrenheit, like some US thermodynamics texts.

-40 is the one temperature where Celsius and Fahrenheit are equal: -40 °C = -40 °F. A useful checkpoint when verifying a conversion routine.