Delisle to Celsius Converter

About this calculator

The Delisle scale was devised in 1732 by French astronomer Joseph-Nicolas Delisle and, unusually, runs backwards from the scales we use today: it sets 0°De at the boiling point of water and 150°De at its freezing point, so a Delisle reading falls as temperature rises. It was used for weather observation in Russia for roughly a century after Delisle brought it to the St. Petersburg Academy of Sciences, before being displaced by Celsius.

Because Delisle degrees run in the opposite direction and use a different span (150° instead of Celsius's 100° between the same two reference points), the conversion is inverted: C = 100 − D × (2/3), and D = (100 − C) × 1.5. This calculator converts between the two scales in either direction.