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History

Why Does the US Use Fahrenheit? (And Who Else Does)

Gizmoop Team · 7 min read · May 22, 2026

The US uses Fahrenheit because the British colonies adopted it in the 1700s and the US never legally required conversion to Celsius. Even when Britain itself switched to Celsius in the 1960s and 70s, the US opted to keep Fahrenheit through inertia, cost, and lack of political demand. Today, about 335 million people primarily use Fahrenheit, with the US accounting for nearly all of them.

Who invented Fahrenheit?

Daniel Gabriel Fahrenheit was a Polish-born Dutch physicist who in 1724 published a temperature scale using a mercury thermometer. He fixed three reference points: 0°F (the freezing point of a brine solution of water, ice, and ammonium chloride, the coldest temperature he could reliably reproduce), 32°F (the freezing point of pure water), and 96°F (his estimate of human body temperature, later refined to 98.6°F). The scale was popular in Britain and its colonies for over 200 years.

Why 32 and 212 for water?

Water freezes at 32°F and boils at 212°F at sea level. The difference is exactly 180 degrees, which is half of 360, a convenient number for navigation and astronomy when the scale was being designed. The 0-100 brine-to-body-temp range gave Fahrenheit "everyday" temperatures running from very cold to very hot in a 0-100 frame. Some argue this is the scale's greatest strength: human-scaled and intuitive for weather.

Celsius arrives

Swedish astronomer Anders Celsius proposed his centigrade scale (later renamed Celsius) in 1742. He originally inverted it: 100° was freezing, 0° was boiling. After his death, the scale was flipped to the modern form. Celsius uses water's phase changes as anchors (0°C freezing, 100°C boiling) and divides the range into 100 equal degrees. This decimal-friendly structure appealed to scientists immediately.

The metric system absorbs Celsius

When France codified the metric system in the 1790s, Celsius was the obvious temperature companion to meters and grams. Most of Europe adopted both throughout the 1800s. By 1900, Celsius was the global scientific standard. Britain, the original home of Fahrenheit, switched its weather forecasts to Celsius in 1962. Australia, Canada, India, and most of the former British Empire followed in the 1970s.

The US opt-out

The US considered conversion through multiple acts of Congress. The Metric Act of 1866 made metric legal but not mandatory. The Metric Conversion Act of 1975 created a board to encourage conversion without requiring it. The board produced confused recipe labels (grams alongside ounces), bilingual road signs, and a generation of students who learned both systems. President Reagan abolished the board in 1982 when no measurable conversion was happening.

The result: US weather forecasts, thermostats, ovens, refrigerators, and recipe books stayed in Fahrenheit. Only US science, medicine, and military operations use Celsius. The cultural split is generational and contextual: an American doctor prescribes in Celsius and grams; the same person checks the weather in Fahrenheit and drives in miles.

Countries that still use Fahrenheit

The US is the dominant Fahrenheit country. Others include the Bahamas, the Cayman Islands, Belize, Palau, the Federated States of Micronesia, the Marshall Islands, and Liberia. Liberia is interesting: founded by freed American slaves in the 1820s, it inherited US measurement standards. The Caribbean and Pacific island holdouts have small populations and close US trade ties.

Is Fahrenheit "better" for weather?

Defenders argue yes, on two grounds. First, Fahrenheit's 0-100 range roughly matches the "very cold to very hot" range of everyday weather (0°F is about -18°C, very cold; 100°F is about 38°C, very hot). Second, Fahrenheit's smaller degree size means more granular weather descriptions (a 75°F day feels different from a 72°F day; the equivalent 24°C and 22°C feel closer).

Critics counter that Celsius is just as intuitive once you grow up with it. Most of the world reports weather in single Celsius degrees (22°C, 23°C, 24°C) and finds the precision adequate. The defense of Fahrenheit on weather grounds is mostly a defense of habit.

The quick conversion math

Celsius to Fahrenheit: multiply by 1.8 and add 32. So 20°C × 1.8 = 36, plus 32 = 68°F. Fahrenheit to Celsius: subtract 32, divide by 1.8. So (68 − 32) / 1.8 = 20°C. Memorable conversions: 0°C = 32°F (freezing). 10°C = 50°F. 20°C = 68°F (cool). 25°C = 77°F (warm). 30°C = 86°F (hot). 37°C = 98.6°F (body). 100°C = 212°F (boiling).

The likely future

The US will almost certainly not mandate a Celsius switch in any foreseeable timeframe. The cost is enormous, the public demand is zero. What may happen: gradual bilingualism, with weather apps showing both scales, and younger Americans (raised with metric in school and on the internet) increasingly comfortable with Celsius for international travel. Other countries went through this transition over decades; the US may simply take longer.

Frequently asked questions

The US uses Fahrenheit because the British colonies adopted it from England in the 1700s and the US never required conversion. When Britain switched to Celsius in the 1960s and 70s, the US considered conversion but chose not to mandate it. Today, Fahrenheit is deeply embedded in weather forecasts, thermostats, ovens, and everyday speech.

The US, the Bahamas, the Cayman Islands, Belize, Palau, the Federated States of Micronesia, the Marshall Islands, and Liberia. Almost all of these are former US or British territories or have close US ties. The total population using Fahrenheit primarily is about 335 million, with the US accounting for over 95 percent of that.

Daniel Gabriel Fahrenheit, a Polish-born Dutch physicist, in 1724. He set 0°F at the freezing point of a brine solution (the coldest temperature he could reproducibly create in his lab) and 96°F at his estimate of body temperature. Later refinements set water freezing at 32°F and boiling at 212°F, exactly 180 degrees apart. The scale is genuinely a clever invention; it just lost to Celsius for global use.

Some advocates argue Fahrenheit is more "human-scaled" for weather: 0°F is "very cold" and 100°F is "very hot", which roughly matches everyday temperature experience. Celsius compresses everyday temperatures into a smaller range (most weather is -10°C to 35°C). This is mostly a matter of habit; people who grew up with Celsius find it equally intuitive.

Britain officially switched to Celsius for weather forecasts in 1962 (BBC adopted it for broadcasts) and completed the transition through the 1970s. Older Britons still think in Fahrenheit; younger Britons in Celsius. This generational split is common in countries that switched as adults.

The Metric Conversion Act of 1975 made metric (including Celsius) legal in the US but voluntary. Without legal force, weather services, manufacturers, and educators had no reason to spend money switching. President Reagan disbanded the Metric Board in 1982. Without a mandate, the conversion never happened.

Multiply Celsius by 1.8 and add 32. So 20°C × 1.8 + 32 = 68°F. For mental math: double the Celsius and add 30 for a quick estimate (this overestimates by a few degrees). 20°C × 2 + 30 = 70°F (close to the exact 68°F).

Almost certainly not as a mandate. The political cost is high (every weather forecast, thermostat label, and recipe would need conversion), the economic cost is in billions, and there is no public demand. What is happening gradually: US science, medicine, and military all use Celsius internally. The US could eventually become bilingual, with Celsius alongside Fahrenheit, but a wholesale switch is unlikely.