Convert Delisle to Kelvin easily.

Imagine you’re reading an 18th-century Russian weather report and stumble upon a temperature listed as “150°De.” Your first thought? “Is this a typo?” Not quite. You’ve just encountered the Delisle scale, one of history’s most fascinating temperature systems. While modern science relies on Kelvin for absolute measurements, understanding how to convert between these scales connects us to scientific history, and occasionally helps decode old texts. Let’s explore this unusual conversion together.

Unit definitions

What is a Delisle (°De)?

Description: Created in 1732 by French astronomer Joseph-Nicolas Delisle, this scale originally set boiling water at 0°De and increased as temperatures dropped. Later flipped, it became Russia’s primary temperature standard for nearly a century.
Symbol: °De
Common uses: Historical meteorology, 18th-century scientific literature
Definition: Based on mercury expansion, with water boiling at 0°De (after inversion) and freezing at 150°De under standard atmospheric pressure.

What is a Kelvin (K)?

Description: The SI base unit for thermodynamic temperature, essential in physics and chemistry. Unlike Celsius or Fahrenheit, it doesn’t use “degrees.”
Symbol: K
Common uses: Scientific research, astronomy, materials science
Definition: 1/273.16 of the thermodynamic temperature of water’s triple point. Absolute zero (0 K) is the theoretical absence of thermal energy.

Conversion formula

To convert Delisle to Kelvin:
K = 373.15 - (°De × 2/3)

Breaking it down:

1. Start with 373.15 K (equivalent to 100°C, water’s boiling point)
2. Subtract two-thirds of the Delisle value
3. Result is temperature in Kelvin

Example calculations

Example 1: Convert 100°De to Kelvin
373.15 - (100 × 2/3) = 373.15 - 66.666... ≈ 306.48 K

Example 2: Convert 300°De to Kelvin
373.15 - (300 × 0.6667) = 373.15 - 200 = 173.15 K (Note: This is 100°C below freezing, showing Delisle’s inverted nature)

Conversion tables

Delisle to Kelvin (common values)

Kelvin to Delisle (common values)

From observatories to absolute zero: A temperature tale

Joseph-Nicolas Delisle didn’t set out to create a lasting temperature standard. His 1732 mercury thermometer scale was designed for astronomical observations in Saint Petersburg, where he’d been invited by Peter the Great. The original version had boiling water at 0°De and 2400 increments to mercury’s freezing point, practical for Russia’s cold climate but bewildering to outsiders.

The scale’s inversion (later adjusted so freezing water became 150°De) made it popular in 18th-century Russia. Meteorological stations used Delisle thermometers exclusively until Celsius gained dominance in the 1820s. Meanwhile, William Thomson (Lord Kelvin) developed his absolute scale in 1848 while studying heat engines, forever changing how science measures thermal energy.

Interesting facts

1. A temperature difference of 1°De equals 2/3 Kelvin. One of the largest degree increments among historical scales.
2. At 0 K (-273.15°C), particles theoretically stop moving entirely.
3. Delisle thermometers often had 2400 divisions between boiling and freezing points for extreme precision.
4. The Kelvin scale was redefined in 2019 using the Boltzmann constant rather than water’s triple point.
5. Some surviving Delisle thermometers are considered valuable antiques, with one selling for €8,400 in 2019.

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