Unit conversion
Temperature Converter
Converts temperature, where the offset matters as much as the scale.
Result
Temperature scales have different zero points, so they convert with an offset as well as a factor. You cannot simply multiply.
Get a Free Business AuditHow the calculation works
Fahrenheit to Celsius subtracts thirty-two and multiplies by five ninths; Celsius to Fahrenheit multiplies by nine fifths and adds thirty-two, so twenty degrees Celsius is sixty-eight Fahrenheit. Kelvin is Celsius plus the absolute offset. Temperature conversion is not a single multiplication because the scales have different zero points.
What moves the number
- Which scales are being converted between.
- Whether the figure is a temperature or a temperature difference.
- Precision required.
- Absolute scales for thermodynamic calculations.
Where this one goes wrong
A temperature difference converts differently from a temperature, because the offset does not apply to a difference: a rise of ten degrees Celsius is a rise of eighteen Fahrenheit rather than fifty, and applying the full formula to a difference produces a nonsense figure. Decide which you have. Thermodynamic calculations also require an absolute scale, since ratios of temperature are meaningless on a scale whose zero is arbitrary.
Before you quote
- Distinguish a temperature from a temperature difference.
- Use an absolute scale for any ratio or thermodynamic calculation.
- Apply the offset only to absolute temperatures.
Questions
About this calculator
How do I convert a temperature difference?
By the scale factor only, without the offset. A rise of ten degrees Celsius is a rise of eighteen Fahrenheit, not fifty. Applying the full conversion formula to a difference produces a nonsense figure.
Why is temperature conversion not a single multiplication?
Because the scales have different zero points. Fahrenheit and Celsius both place zero arbitrarily, so converting between them requires an offset as well as a scale factor, unlike length or weight.
When is Kelvin needed?
In any calculation involving a ratio of temperatures, since ratios are meaningless on a scale whose zero is arbitrary. Thermodynamic and gas law calculations require an absolute scale for exactly that reason.
Common temperature conversions
| From | Equals |
|---|---|
| 1 Fahrenheit | -17.222222 Celsius |
| 1 Fahrenheit | 1 Fahrenheit |
| 1 Fahrenheit | 255.927778 Kelvin |
| 1 Fahrenheit | 460.67 Rankine |
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How to use this calculator
- Value. Enter your own figure; the page starts at 72.
- From. Enter your own figure; the page starts at Fahrenheit.
- To. Enter your own figure; the page starts at Celsius.
The result updates as you type, so you can try a figure, see what it does to converted value, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Value | 72 |
| From | Fahrenheit |
| To | Celsius |
What comes out
| Result | Value |
|---|---|
| Converted value main result | 22.2222 |
| Conversion factor | 0.555556 |
72 Fahrenheit equals 22.2222 Celsius.
How sensitive the answer is
Holding everything else steady and changing only value, this is what happens to converted value. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Value | Converted value |
|---|---|
| 36 | 2.2222 |
| 54 | 12.2222 |
| 72 example above | 22.2222 |
| 108 | 42.2222 |
| 144 | 62.2222 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Value
- A number, starting at 72.
- From
- Choose from Celsius, Fahrenheit, Kelvin, Rankine.
- To
- Choose from Celsius, Fahrenheit, Kelvin, Rankine.
What the results tell you
| Result | What it is |
|---|---|
| Converted value | The headline result. A number. |
| Conversion factor | A number. |
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