| Fahrenheit (°F) | Kelvin (K) |
|---|
To convert Fahrenheit to Kelvin, subtract 32, multiply by 5/9, then add 273.15. This combines the °F→°C and °C→K steps:
Absolute zero is 0 K = −459.67°F. No temperature can go below 0 K.
Key temperature landmarks in Fahrenheit and Kelvin:
To convert Fahrenheit to Kelvin, first convert to Celsius by subtracting 32 and multiplying by 5/9, then add 273.15. The full formula is: K = (°F − 32) × 5/9 + 273.15. For example, 212°F (boiling point of water) = (212 − 32) × 5/9 + 273.15 = 100 + 273.15 = 373.15 K. Room temperature at 68°F = 293.15 K.
Absolute zero — the lowest physically possible temperature — is 0 K, which equals −459.67°F. To go back from Kelvin to Fahrenheit: °F = (K − 273.15) × 9/5 + 32.
This conversion is most commonly needed in scientific and engineering contexts where US Fahrenheit measurements need to be expressed in SI units for calculations. The Kelvin scale is required by physics and chemistry formulas involving absolute temperature — such as the Ideal Gas Law, Stefan-Boltzmann law, and Boltzmann constant calculations. It is also used in astronomy (star surface temperatures), materials science, and cryogenics.
Use the formula: K = (°F − 32) × 5/9 + 273.15. First subtract 32, then multiply by 5/9 to get Celsius, then add 273.15 to get Kelvin. For example, 98.6°F = (98.6 − 32) × 5/9 + 273.15 = 37 + 273.15 = 310.15 K.
Absolute zero (0 K) equals −459.67°F. This is the theoretical minimum temperature — the point at which all molecular motion ceases. Using the inverse formula: (0 − 273.15) × 9/5 + 32 = −491.67 + 32 = −459.67°F.
32°F (the freezing point of water) equals 273.15 K. Using the formula: (32 − 32) × 5/9 + 273.15 = 0 + 273.15 = 273.15 K. Similarly, 212°F (boiling point) = 373.15 K.
Kelvin is the SI base unit of temperature and starts at absolute zero. This makes it essential for thermodynamic equations where temperature must be absolute (not relative). Many physics formulas break down if you use Celsius or Fahrenheit, which have arbitrary zero points.
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