× 9/5 ± 32, Kelvin via ±273.15. The formula line under the result is that exact factor for the pair you picked.
These match the CATS table on this page:
Most measurement categories convert through a single SI base unit: your value is multiplied by a 'from' factor to reach that base unit, then divided by a 'to' factor to reach your target unit — for example, 1 inch = 0.0254 metres, or 1 pound = 0.45359237 kilograms, using internationally defined exact conversion constants.
Temperature is the one category that doesn't work this way, since Celsius, Fahrenheit, and Kelvin don't share a common zero point — Celsius to Fahrenheit uses × 9/5 + 32, and Kelvin is simply Celsius plus 273.15, both affine (offset) conversions rather than a simple multiplication.
The formula line shown underneath each result is the exact factor used for that specific pair of units, so you can see precisely how the number was reached rather than just trusting a black-box result — useful for double-checking a conversion or learning the underlying factor yourself.
Because Celsius, Fahrenheit, and Kelvin scales don't share a common zero point the way metric and imperial length or weight units do. Temperature conversions need an offset (addition or subtraction) as well as a multiplication, unlike a simple ratio-based conversion.
They use internationally defined exact constants where they exist — for example, 1 inch is defined as exactly 0.0254 metres, and 1 pound is exactly 0.45359237 kilograms, so results are as accurate as the underlying standard allows.
It shows the exact multiplication or conversion factor used to get from your source unit to your target unit, so you can see the actual math rather than just the final number.
Length, weight, temperature, volume, and other common measurement categories — each using the appropriate conversion method (a single SI-base factor for most, an affine formula specifically for temperature).