Celsius to Fahrenheit Converter
Convert temperatures between Celsius, Fahrenheit, and Kelvin. Includes common reference points and conversion formulas.
Celsius to Fahrenheit Converter
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Formula: F = (C x 9/5) + 32 | C = (F - 32) x 5/9 | K = C + 273.15
Worked example โ 350 degrees F = 176.67 degrees C = 449.82 K
Formula
F = (C x 9/5) + 32 | C = (F - 32) x 5/9 | K = C + 273.15
The Celsius and Fahrenheit scales have different zero points and degree sizes. Fahrenheit has 180 degrees between water's freezing (32 degrees F) and boiling (212 degrees F) points, while Celsius has 100 degrees (0 degrees C to 100 degrees C). The ratio 9/5 (or 1.8) converts the degree size, and adding/subtracting 32 accounts for the offset. Kelvin starts at absolute zero and uses the same degree size as Celsius.
Worked Examples
Example 1: Cooking Temperature Conversion
Problem:Convert an oven temperature of 350 degrees F to Celsius for a European recipe.
Solution:C = (F - 32) x 5/9 C = (350 - 32) x 5/9 C = 318 x 5/9 C = 176.67 degrees C Round to nearest 5: approximately 175 degrees C (Gas Mark 4)
Result:350 degrees F = 176.67 degrees C = 449.82 K
Example 2: Weather Temperature
Problem:The forecast says 28 degrees C. What is that in Fahrenheit?
Solution:F = (C x 9/5) + 32 F = (28 x 9/5) + 32 F = (28 x 1.8) + 32 F = 50.4 + 32 F = 82.4 degrees F This is a warm summer day.
Result:28 degrees C = 82.4 degrees F = 301.15 K
Frequently Asked Questions
How do I convert Fahrenheit to Celsius?
To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit temperature and then multiply by 5/9 (or divide by 1.8). The formula is: C = (F - 32) x 5/9. For example, to convert 72 degrees Fahrenheit: 72 - 32 = 40, then 40 x 5/9 = 22.22 degrees Celsius. A quick estimation trick: subtract 30 and divide by 2 (72 - 30 = 42, 42/2 = 21, close to the actual 22.22).
What is the Kelvin scale and when is it used?
The Kelvin scale is the SI (International System of Units) standard for temperature measurement. It starts at absolute zero (0 K = -273.15 degrees C), the lowest theoretically possible temperature where all molecular motion stops. Kelvin is used in science, engineering, color temperature (photography/lighting), and thermodynamics. Unlike Celsius and Fahrenheit, Kelvin uses no degree symbol โ you say '300 Kelvin' not '300 degrees Kelvin.' Each Kelvin increment equals one Celsius degree.
At what temperature are Celsius and Fahrenheit equal?
Celsius and Fahrenheit scales intersect at exactly -40 degrees. At this temperature, -40 degrees C equals -40 degrees F. You can verify: (-40 x 9/5) + 32 = -72 + 32 = -40 degrees F. This is also a useful fact for double-checking conversion formulas. Above -40, Fahrenheit values are always higher than Celsius values for the same temperature. Below -40, Fahrenheit values are lower.
Why does the US use Fahrenheit while most countries use Celsius?
The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in 1724 and was widely adopted in English-speaking countries. The Celsius scale (originally called centigrade) was developed by Anders Celsius in 1742 with the more intuitive 0-100 range between water's freezing and boiling points. Most countries adopted Celsius during metrication in the 1960s-70s. The US, along with a few territories, retained Fahrenheit for everyday use due to cultural familiarity and the cost of conversion, though Celsius is used in US scientific contexts.
What is the difference between converting a temperature and converting a temperature difference?
A reading needs both the scale factor and the offset, but a difference or interval needs only the factor. A rise of 10 degrees Celsius is a rise of 10 x 1.8 = 18 degrees Fahrenheit, not 50. Adding 32 to an interval is a classic error that turns a small change into a large one. The same rule applies to rates and tolerances, so a thermostat deadband of 0.5 degrees C is 0.9 degrees F, and a Celsius interval converts to Kelvin one for one.
What is the Rankine scale and how does it relate to Fahrenheit?
Rankine is the absolute scale built on Fahrenheit degrees, the way Kelvin is built on Celsius degrees. Zero Rankine is absolute zero, and the conversion is R = F + 459.67. Because a Rankine degree equals a Fahrenheit degree, 1 K equals 1.8 R. Rankine still appears in thermodynamics and combustion work done in US customary units, where gas law and cycle efficiency calculations require an absolute temperature rather than a scale with an arbitrary zero.
Why is the Kelvin offset 273.15 rather than a round 273?
The offset comes from where the Celsius zero sits relative to absolute zero, and that position was fixed so the two scales share the same degree size while the ice point of water lands near 0 degrees Celsius. The value 273.15 is exact by definition of the Celsius scale, not a rounded measurement, so K = C + 273.15 introduces no error. Using 273 instead is an approximation that costs 0.15 K, which is negligible for weather but not for calorimetry or gas law work.
How should I convert oven temperatures for a recipe?
Convert with the exact formula first, then round to the nearest setting the oven actually offers, since dials and digital controls usually step in 5 or 10 degree increments and ovens cycle around a setpoint anyway. 350 degrees F converts to 176.67 degrees C, which is set as 175 degrees C. Rounding after conversion rather than before avoids compounding error, and remember fan or convection ovens are commonly run lower than the same conventional setting.
Why do the same weather swings look larger in Fahrenheit?
A Fahrenheit degree is smaller: there are 180 Fahrenheit degrees between the freezing and boiling points of water where Celsius has 100, so one Celsius degree spans 1.8 Fahrenheit degrees. Any real change therefore produces 1.8 times as many numbers on the Fahrenheit scale. A day warming from 18 to 28 degrees Celsius warms from 64.4 to 82.4 degrees Fahrenheit, an 18 degree move that describes exactly the same physical change as the 10 degree Celsius move.
How do I convert between Celsius, Fahrenheit, and Kelvin?
Celsius to Fahrenheit: multiply by 9/5 and add 32. Fahrenheit to Celsius: subtract 32 and multiply by 5/9. Celsius to Kelvin: add 273.15. Key reference points: water freezes at 0C/32F/273.15K and boils at 100C/212F/373.15K.
References
Background & Theory
Fahrenheit = Celsius x 9/5 + 32, and Celsius = (Fahrenheit - 32) x 5/9 - both are exact. Temperature is the one common conversion that is not a single multiplying factor, because the two scales have different zero points as well as different degree sizes.
Conversion reference table
| Conversion | Equivalent | Exact or rounded? |
|---|---|---|
| 0 degrees Celsius | 32 degrees Fahrenheit = 273.15 K | Exact (water freezes) |
| 100 degrees Celsius | 212 degrees Fahrenheit = 373.15 K | Exact |
| 37 degrees Celsius | 98.6 degrees Fahrenheit | Exact conversion of a rounded body temperature |
| -40 degrees Celsius | -40 degrees Fahrenheit | Exact - the scales cross here |
| 1 Celsius degree of interval | 1.8 Fahrenheit degrees = 1 kelvin | Exact |
| Absolute zero | -273.15 C = -459.67 F = 0 K | Exact by definition |
Watch the difference between a temperature and a temperature interval. A reading of 20 C is 68 F, but a rise of 20 C is a rise of 36 F, because the +32 offset applies to the reading and not to the change. The kelvin shares the Celsius degree size exactly, so a Celsius interval and a kelvin interval are interchangeable, and since the 2019 SI redefinition the kelvin is fixed by an exact value of the Boltzmann constant.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator ยท Editorial policy
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