Calculator
What the Delisle Converter does
Delisle Converter: converts Delisle to Celsius through temperature's base unit, so the result is exact rather than rounded. Example: 25 °De = 83.33333333 °C.
The inputs are Temperature, From and To; the output is Result, How it was calculated and Reverse conversion. There is no submit step; the numbers move as you adjust them.
It is mostly used by students converting units for homework. Unit mistakes are quietly expensive. They have wrecked spacecraft and ruined recipes alike.
Nothing leaves the tab. You can watch your browser network panel while you use it and see for yourself.
The field reference, the method and a worked example using the default inputs follow the tool itself.
What do the Delisle Converter fields mean?
The Delisle Converter uses 3 inputs. The starting figures are ordinary, not edge cases, so they make a sensible baseline.
| Field | What to enter | Default |
|---|---|---|
| Temperature | required | 25 |
| From | choose from Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré) or Delisle (°De) | Delisle (°De) |
| To | choose from Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré) or Delisle (°De) | Celsius (°C) |
How does the Delisle Converter work?
Temperature scales differ in where zero sits as well as in step size, so this is an offset plus a scale, not a single multiplying factor. That is why you cannot convert a temperature *difference* with the same expression you use for a temperature.
Where a unit has an exact legal definition, that exact value is used rather than a rounded one. The 1959 international agreement fixing the inch at 25.4 mm is the best-known example; the same principle applies throughout.
Worked example
These are the values the Delisle Converter loads by default, and the result it produces from them. The defaults produce the result shown here; change any of them and the answer moves.
| Temperature | 25 |
|---|---|
| From | Delisle (°De) |
| To | Celsius (°C) |
| Result | 83.33333333 °C |
|---|---|
| How it was calculated | 25 °De → 83.33333333 °C (via °C) |
| Reverse conversion | 112.5 °De (if you meant 25 °C) |
The Delisle scale
The Delisle scale is a historical curiosity: it runs backwards relative to every other common scale, with 0°De set at the boiling point of water and 100°De at the freezing point. Increasing temperature means a decreasing Delisle number.
Worth knowing
- It was devised in 1732 by French astronomer Joseph-Nicolas Delisle for a mercury thermometer, and was used for a time in Russia (Delisle worked at the St. Petersburg Academy of Sciences) before being superseded by more conventional scales.
- The inverted design reflects an 18th-century convenience for weather measurement: since Delisle originally calibrated from the boiling point downward, colder days simply produced larger, easier-to-read positive numbers.
- It has no practical modern use outside of historical and educational interest. This converter exists mainly for completeness and for anyone working with historical Russian scientific instruments or records.
Definitions: BIPM SI Brochure · NIST reference on units
How to use it
- Key in Temperature.
- Pick a value for From: the options are Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré) or Delisle (°De).
- Pick a value for To: the options are Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré) or Delisle (°De).
- No confirmation step: what you type is what gets calculated.
- Read Result, How it was calculated and Reverse conversion in the results panel.
- If you need a record, Copy Link saves the inputs and Print produces a clean page.
What this tool does not do
- Factors use the internationally agreed definitions; some industries round them differently.
- Repeated conversions compound rounding, so convert once from the original value where you can.
- The tool answers exactly the question it is given; it cannot know the context around your numbers.
- A plausible-looking answer from the wrong input is still the wrong answer: verify the fields first.
Frequently asked questions
Only Temperature, From and To. A starting value is in place for each, so the quickest approach is to replace the one number you actually care about.
With the values loaded when the page opens, result comes out as 83.33333333 °C. Edit any input and that figure moves with it.
No record is kept. We never receive what you type, so there is nothing on our side to retain.
No cost and no account. Use it as often as you like.
It is accurate to the method shown. Rounding only affects what is displayed, never what is computed.