The Delisle scale is thermometry's oddball: invented in 1732 by French astronomer Joseph-Nicolas Delisle, it counts backwards from water's boiling point, so hotter means a lower number and ice water scores a whopping 150°De. Converting from Fahrenheit uses the formula (212 − °F) × 5/6. Type 68 into the Fahrenheit (°F) box — American room temperature — and the Delisle (°De) readout shows 120. The anchors tell the story: 212°F (boiling) is 0°De, the scale's zero, while 32°F (freezing) is 150°De. Russia used Delisle for about a century, so old Russian scientific papers quote temperatures that look like nonsense until converted. Each Fahrenheit degree is worth five-sixths of a Delisle degree, and the inversion means you subtract from 212 instead of adding from 32. Nobody's thermostat speaks Delisle today, but for history-of-science buffs and conversion-puzzle fans, this is the strangest scale in the drawer. Each Fahrenheit degree equals five-sixths of a Delisle degree, so everyday temperatures land in a comfortable two-to-three-digit range instead of ballooning into the thousands.

With the pre-filled defaults — Fahrenheit (°F) 32 — the Fahrenheit to Delisle Converter returns Delisle (°De) 150.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.