Convert Rankine to Delisle faster than a speeding comet

Ever found yourself staring at a 19th-century Russian scientific manuscript or troubleshooting a vintage aerospace system, only to encounter temperatures in Delisle or Rankine? These two scales test even seasoned professionals. Let’s break down their quirks and make conversions feel like a leisurely stroll through a physics museum.

Unit definitions

What is a Rankine (°R)?

The Rankine scale, named after Scottish engineer William Rankine, shares its degree size with Fahrenheit but starts at absolute zero (-459.67°F). It’s the go-to choice for American engineers working with thermodynamic equations, particularly in power generation and aerospace systems. You’ll see it in technical documents for legacy spacecraft and steam turbine specifications.

Symbol: °R
Common uses: Thermodynamic calculations, US engineering systems
Definition: 0°R = absolute zero, 1°R = 1°F

What is a Delisle (°De)?

Created by French astronomer Joseph-Nicolas Delisle in 1732, this inverted scale originally set boiling water at 0°De and increased numbers as temperatures dropped. Later flipped to match other scales, it still maintains its unique decreasing pattern. Fun fact: Delisle’s mercury thermometers were so accurate they became standard equipment in Russian meteorological stations for over 100 years.

Symbol: °De
Common uses: Historical records, specialty thermometry
Definition: (100°C - temperature) × 3/2

Conversion formula

The mathematical bridge between these scales looks deceptively simple:
Delisle = (671.67 - Rankine) × 5/6

This formula works because:

1. 671.67°R equals 212°F (water’s boiling point)
2. Subtracting your Rankine value reverses the scale
3. Multiplying by 5/6 converts Rankine degrees to Delisle’s larger units

Example calculations

Converting 500°R to Delisle:
(671.67 - 500) = 171.67
171.67 × 5/6 = 143.06°De

Converting 1000°R to Delisle:
(671.67 - 1000) = -328.33
-328.33 × 5/6 = -273.61°De

Conversion tables

Rankine to Delisle

Delisle to Rankine

From steam engines to space shuttles: A temperature tale

The Rankine scale’s 1859 debut coincided with the Second Industrial Revolution, becoming essential for calculating steam engine efficiency. Meanwhile, Delisles 1732 creation outlived its inventor through Russian winter studies. During the Space Race, NASA engineers constantly converted between Rankine (for Saturn V rocket specs) and Delisle (when interpreting Soviet research). This conversion kept both sides guessing during the Cold War’s scientific espionage era.

Joseph-Nicolas Delisle would probably chuckle knowing his temperature scale, initially calibrated using St. Petersburg’s harsh winters, now helps historians decode climate patterns from centuries past. The Rankine scale’s persistence in US engineering shows how measurement systems become entrenched, even when “better” alternatives exist.

Interesting facts

1. The coldest recorded temperature in Delisle (-273.15°De) matches absolute zero
2. Russia’s Academy of Sciences paid Delisle 10,000 rubles (≈$200,000 today) for his thermometer design
3. Rankine’s original papers used water’s triple point as 491.688°R before later standardization
4. Some Antarctic research stations still keep Delisle thermometers as backup instruments
5. The Mars Climate Orbiter failure (1999) involved unit conversion errors, though not Rankine/Delisle

FAQ