Convert Fahrenheit to Celsius

How to convert degrees Fahrenheit to degrees Celsius

In decimal form, the exact Fahrenheit-to-Celsius relationship reads °C = °F × 0.555556 − 17.7778. The two scales are locked together by definition, so any Fahrenheit reading maps to a single Celsius value, with rounding of the constants as the only source of fuzz. The decimals look less tidy than in the reverse direction, but the arithmetic is just as mechanical.

1. Multiply the Fahrenheit temperature by 0.555556.
2. Subtract 17.7778.
3. What remains is the temperature in degrees Celsius.

Worked example: a US heat advisory at 100 °F works out as 100 × 0.555556 − 17.7778 = 37.7778 °C — a number that immediately reads as dangerous to anyone raised on Celsius.

What is a degree Fahrenheit?

Fahrenheit is the scale on American weather apps, oven dials, thermostats, and medical thermometers, and almost nowhere else in daily use. Its defining quirk is granularity: the span between water freezing and water boiling covers 180 degrees, so each Fahrenheit degree is a finer step than its Celsius counterpart, which is partly why US forecasts feel so precise.

What is a degree Celsius?

The degree Celsius is the temperature unit of the metric world and of the SI, where it is defined exactly through the kelvin. Its round anchors — water freezing at 0 °C and boiling at 100 °C — make it easy to calibrate intuition. Because most forecasts and recipes outside the US assume it, turning Fahrenheit input into Celsius is a daily reflex for travelers and expats.

When you’ll need °F to °C

• Making sense of American weather. A 100 °F heat wave is 37.7778 °C, and a bitter 0 °F cold snap is -17.7778 °C — two conversions that turn a US forecast from abstract to visceral.
• Cooking from US recipes with precise temperatures. Sous-vide instructions at 150 °F mean 65.5556 °C, and candy recipes that say 250 °F mean 121.1111 °C on a metric thermometer.
• Setting up American appliances. US fridge manuals recommend keeping the cabinet around 37 °F, which is 2.7778 °C on a metric-display model.
• Anchoring quick estimates. 50 °F is exactly 10 °C — one of the few clean matches between the scales, and a reliable mental checkpoint for spring and autumn days.
• Judging mild weather. 60 °F is 15.5556 °C and 80 °F is 26.6667 °C, bracketing the range Americans tend to describe as pleasantly warm.