Temperature Converter

Last verified: July 2026

Convert temperatures between Celsius, Fahrenheit, Kelvin, and Rankine scales instantly with real-world thresholds and step-by-step mathematical solutions.

Min: -273.15°CMax: 300°C
Quick Temperature Milestones
CONVERTED TEMPERATURE SCALES
Celsius
25.00°C
Fahrenheit
77.00°F
Kelvin
298.15 K
Rankine
536.67°R
State at 25.0°C: Comfortable Room Temp
100°C (Boil)
37°C (Body)
0°C (Freeze)
-273°C (0 K)
25.0°CComparative Scale
How is this calculated? (View worked mathematical solution)

All conversions are executed using the exact NIST linear thermodynamic scale equations.

T_F = T_C × 1.8 + 32 = 25 × 1.8 + 32 = 45 + 32 = 77°F
Methodology, Constants & NIST References

Our conversion pipeline is built directly on standard physical definitions established by international treaties:

  • NIST Special Publication 811: Establishes the exact Celsius-to-Fahrenheit scaling ratio of 1.8 (9/5) and offset of 32.
  • Absolute Zero Limits: Absolute zero is the theoretical lower limit of thermodynamic temperature (0 Kelvin or -273.15° Celsius). Any input below this limit is flagged as physically invalid.
  • Kelvin Definition: Standardized around Boltzmann constant definitions; no degree symbol is used as it is an absolute scale.

About the Temperature Converter

Temperature is a physical property of matter that quantitatively expresses the concepts of hotness and coldness. It is a measure of the average kinetic energy of the constituent particles (atoms or molecules) within a thermodynamic system. To measure and compare this energy, scientists developed multiple temperature scales: Celsius (°C) and Fahrenheit (°F) are relative scales designed around physical phenomena like the freezing and boiling points of water under standard atmospheric pressure; Kelvin (K) and Rankine (°R) are absolute thermodynamic scales whose zero points coincide with absolute zero—the theoretical state where all classical molecular motion ceases. Converting between these scales is vital in chemistry, meteorology, aerospace engineering, culinary arts, and daily climate observation.

Mathematical Formula & Logic

Temperature conversion formulas utilize linear relationships to map values between scales: 1. Celsius to Fahrenheit: °F = (°C × 9/5) + 32 2. Celsius to Kelvin: K = °C + 273.15 3. Celsius to Rankine: °R = (°C + 273.15) × 9/5 4. Fahrenheit to Celsius: °C = (°F − 32) × 5/9 5. Fahrenheit to Kelvin: K = (°F − 32) × 5/9 + 273.15 6. Fahrenheit to Rankine: °R = °F + 459.67

Step-by-Step Example

Convert 98.6 °F (standard human body temperature) to Celsius and Kelvin: 1. Identify the variables: - Fahrenheit (°F) = 98.6 2. Convert to Celsius using the formula: °C = (°F − 32) × 5/9 °C = (98.6 − 32) × 5/9 °C = 66.6 × 5/9 = 37.0 3. Convert the Celsius result to Kelvin: K = °C + 273.15 K = 37.0 + 273.15 = 310.15 4. Therefore, 98.6 °F is equal to exactly 37.0 °C and 310.15 K.

Reference Data & Values

scale referencecelsiusfahrenheitkelvinrankine
Absolute Zero-273.15 °C-459.67 °F0.00 K0.00 °R
Freezing Point of Water0.00 °C32.00 °F273.15 K491.67 °R
Standard Room Temperature20.00 °C68.00 °F293.15 K527.67 °R
Human Body Temperature37.00 °C98.60 °F310.15 K558.27 °R
Boiling Point of Water100.00 °C212.00 °F373.15 K671.67 °R

Frequently Asked Questions

Multiply the Celsius temperature by 1.8 (or 9/5) and add 32. For example, to convert 20°C: (20 * 1.8) + 32 = 36 + 32 = 68°F.
Subtract 32 from the Fahrenheit temperature, then divide the result by 1.8. For example, to convert 68°F: (68 - 32) / 1.8 = 36 / 1.8 = 20°C.
Simply add 273.15 to the Celsius temperature. For example, 0°C is equal to 273.15 Kelvin. Kelvin is an absolute thermodynamic scale and does not use a degree symbol.
Yes, Celsius and Fahrenheit scales intersect and read exactly the same value at -40 degrees (-40°C = -40°F).
Absolute zero is the theoretical temperature at which all classical molecular motion stops. It is defined as exactly 0 Kelvin (0 K), which is equivalent to -273.15°C and -459.67°F.
The Rankine scale (°R) is an absolute temperature scale that uses Fahrenheit increments. Much like Kelvin is the absolute counterpart to Celsius, Rankine is the absolute counterpart to Fahrenheit, starting at absolute zero.
Kelvin is an absolute scale based on thermodynamics rather than relative physical benchmarks (like freezing and boiling points of water). Thus, the unit of measurement is the kelvin itself (K), rather than a degree of a scale.
At standard sea-level atmospheric pressure, water boils at 373.15 Kelvin, which is equal to 100°C and 212°F.