40°F is equal to 277.039 kelvin.
To convert 40 degrees Fahrenheit to kelvin, first convert Fahrenheit to Celsius, then Celsius to kelvin. Fahrenheit scale has a different zero point and degree size than Celsius, so direct conversion isn’t possible. Using formulas, it’s straightforward to get the kelvin value.
Conversion Tool
Result in kelvin:
Conversion Formula
The conversion from Fahrenheit (f) to kelvin involves two steps. First, subtract 32 from the Fahrenheit value to adjust the zero point difference between Fahrenheit and Celsius. Then multiply by 5/9 to convert the degree size from Fahrenheit to Celsius. Finally, add 273.15 to convert Celsius to kelvin, because kelvin starts at absolute zero, which is -273.15°C.
Formula: K = (F – 32) × 5/9 + 273.15
For 40°F:
- Subtract 32: 40 – 32 = 8
- Multiply by 5/9: 8 × 5/9 = 4.4444
- Add 273.15: 4.4444 + 273.15 = 277.5944 kelvin
Conversion Example
- Convert 70°F to kelvin:
- 70 – 32 = 38
- 38 × 5/9 = 21.1111
- 21.1111 + 273.15 = 294.2611 K
- Convert 0°F to kelvin:
- 0 – 32 = -32
- -32 × 5/9 = -17.7778
- -17.7778 + 273.15 = 255.3722 K
- Convert 100°F to kelvin:
- 100 – 32 = 68
- 68 × 5/9 = 37.7778
- 37.7778 + 273.15 = 310.9278 K
- Convert 25°F to kelvin:
- 25 – 32 = -7
- -7 × 5/9 = -3.8889
- -3.8889 + 273.15 = 269.2611 K
Conversion Chart
| Fahrenheit (°F) | Kelvin (K) |
|---|---|
| 15.0 | 264.2611 |
| 20.0 | 266.4833 |
| 25.0 | 268.7056 |
| 30.0 | 270.9278 |
| 35.0 | 273.1500 |
| 40.0 | 275.3722 |
| 45.0 | 277.5944 |
| 50.0 | 279.8167 |
| 55.0 | 282.0389 |
| 60.0 | 284.2611 |
| 65.0 | 286.4833 |
The chart shows Fahrenheit values from 15.0 to 65.0 and their equivalent kelvin values. To use it, find the Fahrenheit temperature you want to convert, then read across to get the kelvin amount. This way you can quickly see the corresponding temperature in kelvin without calculation.
Related Conversion Questions
- How many kelvin is 40 degrees Fahrenheit?
- What’s the kelvin temperature for 40°F?
- Can 40°F be converted directly to kelvin?
- Is 40°F warmer or cooler than 280 kelvin?
- How to calculate kelvin from 40 degrees Fahrenheit?
- Does 40°F equal 277 kelvin exactly?
- What formula converts 40°F into kelvin?
Conversion Definitions
F (Fahrenheit): Fahrenheit is a temperature scale where water freezes at 32 degrees and boils at 212 degrees under standard conditions. Primarily used in the United States, it divides the range between freezing and boiling of water into 180 equal parts called degrees. It’s based on a historical mercury thermometer scale.
Kelvin: Kelvin is the SI unit for temperature measurement, starting at absolute zero (0 K), where molecular motion stops. It uses the same increment size as Celsius but begins at -273.15°C. Kelvin is used in science for precise temperature measurement, especially in physics and chemistry.
Conversion FAQs
Why do we add 273.15 when converting Celsius to kelvin?
Adding 273.15 shifts the Celsius scale to start at absolute zero, which is the lowest theoretical temperature where particles have minimal motion. Kelvin scale begins at absolute zero, so by adding 273.15 to the Celsius value, you align the zero point correctly.
Can I directly convert Fahrenheit to kelvin without using Celsius?
No, because Fahrenheit and kelvin scales have different zero points and increments. The conversion formula first converts Fahrenheit to Celsius, then adds 273.15 to get kelvin. Direct conversion without this intermediate step would give incorrect results.
What does it mean if the kelvin value is less than 273.15?
Kelvin values less than 273.15 correspond to temperatures below the freezing point of water (0°C). Since kelvin starts at absolute zero, values below 273.15 kelvin represent cold temperatures in Celsius below zero degrees.
Is 40°F considered cold in kelvin terms?
40°F equals about 277 kelvin, which is just above the freezing point (273.15 K). In everyday terms, it’s a cool temperature but not freezing. In kelvin, it is just a few units above freezing, indicating chill but not extreme cold.
Why does the Fahrenheit scale use 32 and 212 for freezing and boiling instead of 0 and 100?
The Fahrenheit scale was designed historically based on several reference points, including the freezing point of a brine solution at 0°F, and the freezing and boiling points of water at 32°F and 212°F. This differs from Celsius, which uses 0 and 100 for freezing and boiling water respectively.