°F to K Converter
Convert Fahrenheit temperatures into Kelvin values
Fahrenheit to Kelvin FAQ
How do you convert Fahrenheit to Kelvin exactly?
The standard formula is: K = (°F − 32) × 5⁄9 + 273.15. First you subtract 32 from the Fahrenheit temperature, then multiply by 5/9 to get °C, and finally add 273.15 to shift from Celsius to Kelvin. For example, 68 °F becomes (68 − 32) × 5/9 + 273.15 = 293.15 K. This calculator applies that °F to K relationship for you and prints the result in a clean, copy-friendly line.
Why do we add 273.15 when converting to Kelvin?
The Celsius and Kelvin scales have the same size degrees, but different zero points. The Kelvin scale starts at absolute zero, the coldest possible temperature, while 0 °C is the freezing point of water. By definition, K = °C + 273.15. After turning Fahrenheit into Celsius with (°F − 32) × 5/9, adding 273.15 shifts the value onto the absolute Kelvin scale used in physics and engineering.
What is absolute zero in °F, °C and K?
Absolute zero is the lowest possible temperature, where thermal motion in matter is at its minimum. It is:
- 0 K by definition
- −273.15 °C
- −459.67 °F
The Kelvin scale is built so that absolute zero is 0 K, which is why scientists prefer it for thermodynamic and statistical mechanics work.
When do I need Kelvin instead of Celsius or Fahrenheit?
Kelvin is the SI base unit for temperature and is widely used in physics, chemistry, climate science, and engineering. Any calculation involving thermodynamic temperature (for example in gas laws, radiation, reaction rates or semiconductor physics) usually expects values in Kelvin. Fahrenheit and Celsius are better for everyday weather and comfort descriptions, while Kelvin is used when absolute temperature matters in formulas.
Can I use this for lab reports and homework?
Yes. Many lab manuals and exam questions specify that temperatures should be reported or calculated in Kelvin. This Fahrenheit to Kelvin converter gives you an accurate value using the same formula you would apply by hand. Always check whether your teacher or institution has any specific rounding rules for final answers.
How many decimal places of Kelvin do I need?
For most lab and engineering work, two decimal places in Kelvin are plenty, especially when your instruments are not more precise than that. For example, 293.15 K might reasonably be reported as 293.2 K. The calculator keeps full precision internally and then prints a tidy result so you can choose how many digits to keep based on your experiment or specification.
What if my starting temperature is already in °C?
If you have Celsius directly, you do not need the Fahrenheit step: you can use K = °C + 273.15 straight away. This page is focused on °F to K for cases where source data or documentation is in Fahrenheit. For more combinations, you can use the dedicated °C↔°F tools or the full temperature conversion calculator.
From everyday Fahrenheit readings to absolute Kelvin values
This °F to K converter is built for situations where data, manuals or instruments show temperatures in Fahrenheit, but your equations or reports need Kelvin. That is common in thermodynamics, gas law work, material science, thermal engineering and parts of climate and atmospheric science. Instead of juggling multiple steps on a calculator, you enter the Fahrenheit value once and get a line like “68 °F = 293.15 K” instantly.
1. One Fahrenheit input, one Kelvin result
The interface is intentionally minimal: a single input box for °F and a result card underneath. You can enter everyday values like 77 °F, or extreme ones such as cryogenic temperatures and high furnace readings, and the converter will still apply the same linear relationship. The output Kelvin value is formatted with sensible precision so it is easy to read on-screen or paste into a lab notebook, spreadsheet or report.
When you need to go in the opposite direction, from Kelvin back to °F, the “Swap Units” button links directly to the K to °F page. That keeps the pair of tools working together so you can flip between absolute and everyday temperature scales without changing your workflow.
2. Linear connection between Fahrenheit, Celsius and Kelvin
The Kelvin scale is anchored at absolute zero and uses the same step size as Celsius: a 1 K change is the same size as a 1 °C change. Fahrenheit uses smaller degree steps and a different zero point. When you combine the relationships °C = (°F − 32) × 5/9 and K = °C + 273.15, you get the compact formula: K = (°F − 32) × 5⁄9 + 273.15. This converter uses that exact relationship, matching scientific calculators and standard reference tables used in teaching and industry.
If you need to work with several temperature units at once, including Rankine or additional engineering scales, the temperature conversion calculator lets you connect multiple units on a single page.
3. Common °F to K values at a glance
Here are some reference points that match the calculator output. They are useful for building a feel for typical temperatures on the Kelvin scale:
| Fahrenheit (°F) | Kelvin (K) |
|---|---|
| −459.67 °F | 0 K (absolute zero) |
| −40 °F | 233.15 K |
| 32 °F | 273.15 K (water freezes) |
| 68 °F | 293.15 K (room temperature) |
| 77 °F | 298.15 K |
| 98.6 °F | 310.15 K (body temperature) |
| 122 °F | 323.15 K |
| 212 °F | 373.15 K (water boils) |
A rough mental shortcut is to subtract 32, halve the result, then add about 273. For precise work, especially where equations depend directly on absolute temperature, this converter replaces that rule of thumb with the exact formula so your numbers stay consistent.
4. Where the °F to K converter shines
You are most likely to rely on this tool in situations such as:
- Physics and thermodynamics — convert Fahrenheit data from older tables into Kelvin for gas laws, engine cycles and radiation formulas.
- Chemistry and reaction kinetics — ensure activation energy and rate equations use temperature in Kelvin even when lab notes or equipment show °F.
- Engineering and process control — translate Fahrenheit-based process readings into Kelvin for simulations, models and documentation.
- Climate and atmospheric science — work with anomalies, lapse rates and radiation balances that require temperatures on an absolute scale.
- Education and homework — double-check manual conversions when teaching or learning about temperature scales and thermodynamics.
Because it follows the officially recognised relationships between Fahrenheit, Celsius and Kelvin, you can return to this Fahrenheit to Kelvin converter any time and get consistent, predictable results that fit both classroom work and real-world lab and engineering tasks.
References and further reading on Fahrenheit and Kelvin
These references explain how the Fahrenheit and Kelvin scales are defined and used:
- Fahrenheit — describes the Fahrenheit temperature scale, its history and fixed points.
- Kelvin — covers the Kelvin scale as the SI base unit of thermodynamic temperature.
- SI Units — Temperature (NIST) — provides official background on temperature units, including the kelvin and its definition.
For critical scientific, industrial or regulatory work, always follow your organisation’s official conversion and rounding procedures when moving between Fahrenheit, Celsius and Kelvin.