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Convert Fahrenheit to Kelvin instantly with our free online calculator. Essential for scientific research, engineering, thermodynamics, and any application requiring the absolute temperature scale.
273.15 K
Water Freezing (32°F)
373.15 K
Water Boiling (212°F)
0 K
Absolute Zero (-459.67°F)
Formula: K = (°F - 32) × 5/9 + 273.15
| Fahrenheit (°F) | Kelvin (K) | Context |
|---|---|---|
| -459.67°F | 0 K | Absolute zero |
| -320°F | 77.59 K | Liquid nitrogen boiling point |
| -40°F | 233.15 K | Where °F and °C are equal |
| 0°F | 255.37 K | Very cold winter day (US) |
| 32°F | 273.15 K | Water freezing point |
| 50°F | 283.15 K | Cool autumn day |
| 68°F | 293.15 K | Room temperature (low) |
| 72°F | 295.37 K | Comfortable indoor temperature |
| 77°F | 298.15 K | Standard temperature (25°C) |
| 98.6°F | 310.15 K | Normal human body temperature |
| 212°F | 373.15 K | Water boiling point |
| 451°F | 505.93 K | Paper autoignition temperature |
| 500°F | 533.15 K | High-temperature oven |
| 1000°F | 810.93 K | Pottery kiln temperature |
| 1832°F | 1273.15 K | Steel forging temperature |
Fahrenheit (°F) is a temperature scale proposed in 1724 by the Polish-German physicist Daniel Gabriel Fahrenheit. On this scale, water freezes at 32°F and boils at 212°F under standard atmospheric pressure, creating a 180-degree span between the two reference points. Fahrenheit is the primary temperature scale used in the United States for everyday weather, cooking, and household thermostats, making it the scale most familiar to roughly 330 million Americans.
Kelvin (K) is the base unit of thermodynamic temperature in the International System of Units (SI). Named after Lord Kelvin (William Thomson, 1824-1907), the scale starts at absolute zero (0 K), the theoretical point where all molecular motion ceases. Unlike Fahrenheit and Celsius, Kelvin does not use the degree symbol -- temperatures are written simply as "300 K," not "300°K." One kelvin increment is exactly equal to one Celsius degree, but the scale is offset by 273.15.
Converting between these scales bridges everyday US temperature measurement with the absolute scale used in physics, chemistry, engineering, and international scientific communication. The formula K = (°F - 32) × 5/9 + 273.15 first converts Fahrenheit to Celsius, then shifts to the Kelvin scale by adding 273.15.
The formula to convert Fahrenheit to Kelvin is: K = (°F - 32) × 5/9 + 273.15. This works by first converting from Fahrenheit to Celsius, then adding 273.15 to shift from the Celsius scale to the Kelvin scale.
Question: Convert a comfortable room temperature of 68°F to Kelvin.
Question: Convert normal human body temperature of 98.6°F to Kelvin.
Question: A pizza oven is set to 450°F. What is that in Kelvin?
For a quick estimate, subtract 32, divide by 2 (instead of multiplying by 5/9), then add 273. This gives you a rough approximation. For example: 212°F → (212 - 32) / 2 + 273 = 90 + 273 = 363 K (exact: 373.15 K). The error from dividing by 2 instead of 1.8 is about 10%, but it is useful for quick mental checks.
| Description | °F | K |
|---|---|---|
| Cold winter day | -10 | 249.82 |
| Freezing point of water | 32 | 273.15 |
| Spring day | 55 | 285.93 |
| Room temperature | 72 | 295.37 |
| Hot summer day | 95 | 308.15 |
| Body temperature | 98.6 | 310.15 |
| Hot tub | 104 | 313.15 |
| Heat wave extreme | 115 | 319.26 |
| Reference Point | °F | K |
|---|---|---|
| Absolute zero | -459.67 | 0 |
| Liquid nitrogen boils | -320.44 | 77.36 |
| Dry ice sublimation | -109.3 | 194.65 |
| Standard lab conditions (STP) | 32 | 273.15 |
| Standard temperature (IUPAC) | 77 | 298.15 |
| Water boils (1 atm) | 212 | 373.15 |
| Lead melts | 621.5 | 600.61 |
| Iron melts | 2800 | 1810.93 |
| Application | °F | K |
|---|---|---|
| Refrigerator | 37 | 275.93 |
| Warm proofing dough | 110 | 316.48 |
| Low oven / slow cook | 250 | 394.26 |
| Moderate oven | 350 | 449.82 |
| Hot oven / pizza | 450 | 505.37 |
| Broiling / grilling | 500 | 533.15 |
| Self-cleaning oven cycle | 900 | 755.37 |
Kelvin is required for all absolute temperature calculations in thermodynamics, including entropy, Gibbs free energy, and the ideal gas law (PV = nRT). Scientists working in the US must convert their Fahrenheit-based measurements to Kelvin for these calculations.
Engineers analyzing thermal stress, heat transfer coefficients, and material properties need Kelvin for accurate calculations. Thermal expansion, blackbody radiation (Stefan-Boltzmann law), and semiconductor physics all require absolute temperature values.
Chemical reaction rates (Arrhenius equation), equilibrium constants, and calorimetry calculations use Kelvin. US-based chemistry labs that measure temperature in Fahrenheit on legacy equipment must convert to Kelvin for proper data analysis and publication.
Scientific journals, international conferences, and collaborative research require Kelvin as the standard temperature unit. American researchers must convert Fahrenheit field data to Kelvin for papers, grants, and peer-reviewed publications.
Order of operations matters. K = (°F - 32) × 5/9 + 273.15. Do the subtraction before the multiplication, then add the Kelvin offset last.
If you get a negative Kelvin value for any real-world scenario, you have made an error. Negative Kelvin is physically impossible. Only temperatures below -459.67°F would theoretically produce negative Kelvin, which cannot exist.
The exact offset between Celsius and Kelvin is 273.15. Rounding to 273 introduces a 0.15 K error, which matters in precise scientific work like calorimetry and thermodynamic calculations.
A common mistake is to add 273.15 to the Fahrenheit value without first converting to Celsius. You must subtract 32 and multiply by 5/9 before adding 273.15.
K = (°F - 32) × 5/9 + 273.15 and K = (°F + 459.67) × 5/9 are mathematically identical. Both are correct, but mixing parts of each formula will give wrong results.
Write "300 K" not "300°K". The SI convention dropped the degree symbol for Kelvin in 1967 because it is an absolute scale, not a relative one like Celsius or Fahrenheit.
Use the formula K = (°F - 32) × 5/9 + 273.15. First subtract 32 from the Fahrenheit value, multiply by 5/9 to convert to Celsius, then add 273.15 to shift to the Kelvin scale. For example, 68°F = (68 - 32) × 5/9 + 273.15 = 293.15 K.
Absolute zero (0 K) equals -459.67°F. This is the lowest physically possible temperature, where all molecular motion theoretically ceases. No object in the universe can be cooled below this point according to the laws of thermodynamics.
Kelvin is an absolute scale starting at absolute zero with no negative values, making it essential for thermodynamic equations, gas laws (PV = nRT), and blackbody radiation calculations. Fahrenheit's arbitrary zero point and negative values complicate scientific formulas.
Water freezes at 273.15 K (32°F or 0°C) under standard atmospheric pressure (1 atm). This is one of the key reference points used to define temperature scales and calibrate thermometers worldwide.
Water boils at 373.15 K (212°F or 100°C) at standard atmospheric pressure. This 100-kelvin span between freezing and boiling is identical to the 100-degree span on the Celsius scale, since both use the same degree size.
No. The Fahrenheit and Kelvin scales never intersect because Kelvin starts at absolute zero (0 K = -459.67°F) and uses smaller degree increments. However, Fahrenheit and Celsius meet at -40°, and Celsius and Kelvin are always offset by exactly 273.15.
Standard room temperature is approximately 293-298 K (68-77°F or 20-25°C). In scientific contexts, "standard temperature" is often defined as exactly 298.15 K (25°C or 77°F) for thermodynamic reference conditions.
The Kelvin scale is an absolute thermodynamic scale, not a relative one. The SI convention reserves the degree symbol for relative scales (°C, °F). Since Kelvin measures absolute thermodynamic temperature from a true zero point, temperatures are expressed simply as "kelvins" (e.g., 300 K, not 300°K).
This calculator uses the standard conversion formula K = (°F - 32) × 5/9 + 273.15, which is mathematically equivalent to K = (°F + 459.67) × 5/9. For laboratory, engineering, or other precision-critical applications, always verify conversions against your institution's calibration standards and measurement protocols.