The Temperature Divide: Fahrenheit vs Celsius

If you're from the United States and you've ever traveled abroad, you've probably experienced that moment of confusion when someone says it's going to be 21 degrees today and you panic about freezing weather, only to realize they're talking about a pleasant spring day. Or maybe you've looked at a European recipe calling for baking at 180 degrees and wondered how you're supposed to cook anything in barely-above-freezing temperatures.

Welcome to the divide between Fahrenheit and Celsius, two different ways of measuring the exact same thing: temperature. Most of the world uses Celsius. The United States, along with a handful of tiny island nations, stubbornly clings to Fahrenheit. And the reasons why are a mix of history, politics, practicality, and plain old resistance to change.

Let's break down how these two scales came to exist, why they're so different, how to convert between them, and why the U.S. refuses to switch despite being almost completely alone in using Fahrenheit.

The Inventor: Daniel Gabriel Fahrenheit and His Dramatic Backstory

The Fahrenheit scale was created by Daniel Gabriel Fahrenheit, a German physicist born in Danzig (now Gdańsk, Poland) on May 24, 1686. And his story is surprisingly dramatic.

When Fahrenheit was just 15 years old, both of his parents died after accidentally eating poisonous mushrooms. The orphaned teenager was taken in by guardians and apprenticed to a merchant in Amsterdam to learn bookkeeping. But Fahrenheit wasn't interested in bookkeeping. He was fascinated by physics, mathematics, and especially glassblowing.

When the Florentine thermometer (an early alcohol-based thermometer invented in Italy) started circulating in Amsterdam, Fahrenheit became obsessed with creating a better, more reliable version. The problem was that he needed money to fund his experiments. His late parents had left him an inheritance, but he couldn't access it until he turned 24.

So he borrowed money. A lot of money. And fell into debt.

His guardians, who were legally responsible for his debt, were furious. They arranged to have him arrested and deported to present-day Indonesia, where he'd work as a laborer for the Dutch East India Company until he paid them back. But when the arrest warrant came through, Fahrenheit had fled the country.

For years, Fahrenheit traveled through Germany, Denmark, Sweden, and Poland, staying one step ahead of Dutch authorities while working on perfecting his thermometer. He learned glassblowing techniques, met with other scientists, and kept refining his designs. When he turned 24, he settled his debts, but he kept traveling and experimenting.

His breakthrough came when he switched from alcohol to mercury as the liquid in his thermometers. Mercury has a much higher boiling point than alcohol, allowing for a wider range of measurable temperatures. And unlike alcohol, mercury doesn't stick to glass, making readings much more accurate.

In 1714, at age 28, Fahrenheit finally achieved his goal: he created two thermometers that gave identical readings in the same conditions. This was revolutionary. Before Fahrenheit, thermometers were inconsistent. You couldn't trust that two different instruments would agree on the temperature. Fahrenheit's innovation made temperature measurement reliable and standardized.

How Fahrenheit Created His Scale

When Fahrenheit designed his temperature scale in 1724, he needed reference points, fixed temperatures that would always be the same so thermometers could be calibrated.

His original system used three points:

0°F: The temperature of a mixture of equal parts water, ice, and ammonium chloride (a type of salt). This created the coldest stable temperature Fahrenheit could reliably reproduce in his lab.

32°F: The temperature at which pure water freezes (without salt).

96°F: The temperature of the human body, measured in the mouth or under the arm.

Why 96 for body temperature? Fahrenheit wanted a scale where common temperatures fell on numbers that could be easily divided. With 0 at the salt-ice mixture and 96 at body temperature, there were 96 degrees between them, which could be divided by 2, 3, 4, 6, 8, 12, and so on. This made it easy to mark divisions on thermometers.

Under this original system, the freezing point of pure water happened to land at 32°F, and the boiling point at 212°F. The gap between freezing and boiling was 180 degrees, another number that divides nicely.

Later, after Fahrenheit's death, the scale was recalibrated slightly. Scientists decided to use the freezing and boiling points of pure water (32°F and 212°F) as the exact reference points instead. This meant body temperature shifted slightly to the now-familiar 98.6°F (which is 37°C converted to Fahrenheit).

The British Royal Society adopted the Fahrenheit scale in 1776, and it spread throughout the British Empire, including to the American colonies.

Enter Anders Celsius: A Simpler System

Just 18 years after Fahrenheit introduced his scale, Swedish astronomer Anders Celsius proposed something different.

Celsius, born in 1701, was interested in atmospheric measurements and weather. In 1742, he developed a scale based on the freezing and boiling points of pure water at sea level, with exactly 100 degrees between them. Simple. Symmetrical. Easy to remember.

But here's a weird detail: Celsius originally set his scale backward. He made 0 degrees the boiling point and 100 degrees the freezing point. Within a year, fellow Swedish scientist Carl Linnaeus (yes, the guy who created the system for naming species) flipped it to the more intuitive version we use today: 0°C for freezing, 100°C for boiling.

The scale was originally called "centigrade" because of the 100-degree span (centi = hundred, grade = steps). In 1948, it was officially renamed "Celsius" to honor its inventor.

The neat 100-degree symmetry of Celsius made it a perfect fit for the metric system, which France was developing in the late 1700s as a way to standardize measurements. By the mid-1800s, most of Europe had adopted the metric system, and Celsius came along with it.

The Key Differences

Let's compare the two scales side by side:

Freezing point of water:

• Fahrenheit: 32°F

• Celsius: 0°C

Boiling point of water:

• Fahrenheit: 212°F

• Celsius: 100°C

Degrees between freezing and boiling:

• Fahrenheit: 180 degrees

• Celsius: 100 degrees

Where they intersect:

• Both scales meet at -40° (so -40°F = -40°C)

Absolute zero (the coldest possible temperature):

• Fahrenheit: -459.67°F

• Celsius: -273.15°C

Average human body temperature:

• Fahrenheit: 98.6°F

• Celsius: 37°C

Because Fahrenheit has 180 degrees between freezing and boiling while Celsius only has 100, each Fahrenheit degree is smaller. Specifically, one Fahrenheit degree equals 5/9 of a Celsius degree. Or looked at the other way, one Celsius degree equals 1.8 Fahrenheit degrees.

The Conversion Formulas

Converting between Fahrenheit and Celsius requires a bit of math because the scales have different zero points and different sized degrees.

To convert Fahrenheit to Celsius:

C = (F - 32) × 5/9

Example: 68°F to Celsius

• 68 - 32 = 36

• 36 × 5/9 = 20°C

To convert Celsius to Fahrenheit:

F = (C × 9/5) + 32

Example: 20°C to Fahrenheit

• 20 × 9/5 = 36

• 36 + 32 = 68°F

Quick mental shortcuts:

• To roughly convert Celsius to Fahrenheit: double it and add 30 (not exact, but close)

• To roughly convert Fahrenheit to Celsius: subtract 30 and divide by 2

Why Most of the World Uses Celsius

By the 1960s, most English-speaking countries still used Fahrenheit. But then things changed rapidly.

The United Kingdom switched to the metric system (including Celsius) in the 1960s and 70s to align with the rest of Europe. Australia, New Zealand, Canada, South Africa, and other former British colonies followed suit during the same period.

The reasons were practical:

• International trade and communication: Using the same measurement system as most other countries makes business, science, and travel easier

• Scientific standardization: The scientific community worldwide uses Celsius (and Kelvin) for research

• Educational simplicity: The metric system, including Celsius, is based on powers of 10, making it easier to teach and learn

• The numbers make sense: Water freezing at 0° and boiling at 100° is more intuitive than 32° and 212°

By the mid-1970s, the metric system (with Celsius) had become the global standard. Today, only a tiny handful of countries still use Fahrenheit for everyday temperature measurements.

Who Still Uses Fahrenheit?

The list is very short:

• United States (and its territories like Puerto Rico, Guam, and the U.S. Virgin Islands)

• Cayman Islands (British territory)

• Palau (Pacific island nation, uses U.S. weather services)

• Federated States of Micronesia (uses U.S. weather services)

• Marshall Islands (uses U.S. weather services)

A few other countries use both systems:

• Belize, Antigua and Barbuda, Saint Kitts and Nevis, Bahamas (use both but increasingly favor Celsius)

• Canada (officially metric, but many Canadians still use Fahrenheit informally, especially in cooking)

That's it. Out of 195 countries, fewer than 10 still use Fahrenheit in any significant way, and the U.S. is by far the largest.

Even Liberia and Myanmar, which used to be listed as Fahrenheit countries, have announced plans to switch to the metric system.

Why Won't America Switch?

The United States has actually tried to go metric. Multiple times.

In 1975, Congress passed the Metric Conversion Act, which was supposed to transition the U.S. to the metric system. It established a Metric Board to coordinate the change. But here's the catch: conversion was voluntary. Businesses and individuals could choose whether to switch.

And most chose not to.

The Metric Board was defunded in 1982. The transition fizzled. America stayed imperial.

So why did the U.S. fail where other countries succeeded?

1. Cost and Infrastructure

Switching would be expensive. Every road sign showing miles would need replacing. Every product label, every speedometer, every ruler in every classroom. Manufacturing equipment, building codes, recipes, thermostats, literally millions of devices and documents would need updating.

Other countries bit this bullet and did it anyway, but the U.S., with its massive size and decentralized decision-making, found it harder to coordinate.

2. Public Resistance

Americans are used to Fahrenheit. When weather forecasters experimented with reporting temperatures in Celsius during the 1970s, people hated it. "21 degrees" sounds cold to American ears. "68 degrees" sounds pleasant. The numbers people grew up with feel right, and new numbers feel wrong.

3. The Fahrenheit Arguments

Defenders of Fahrenheit make some legitimate points:

Fahrenheit is more precise for everyday temperatures. The range of typical weather (0°F to 100°F) covers most conditions people experience, with 0 being really cold and 100 being really hot. In Celsius, typical weather ranges from about -18°C to 38°C, which feels less intuitive.

Fahrenheit degrees are smaller, so you can express temperatures more precisely without decimals. 72°F vs 73°F is a noticeable difference. In Celsius, that's 22.2°C vs 22.8°C. If you round to whole numbers, you lose precision.

Fahrenheit has fewer negative numbers in everyday use. Most places in the U.S. experience temperatures between 0°F and 100°F, staying positive. In Celsius, winter temperatures frequently dip below zero, and some people find negative numbers psychologically discouraging.

4. Scientific Community Already Uses Celsius

Here's a key point: American scientists, engineers, and researchers already use Celsius (and Kelvin) for their work. The National Weather Service uses Celsius internally. NASA uses metric. Drug manufacturers use metric.

So there's less pressure to change for scientific reasons. The problem is mainly for everyday public use, where Americans are comfortable with Fahrenheit and see no compelling reason to switch.

The Celsius Arguments

Of course, defenders of Celsius have responses:

The numbers are more logical. Water freezing at 0° and boiling at 100° is easier to remember and teach than 32° and 212°.

It's the global standard. When 96% of the world's population uses Celsius, sticking with Fahrenheit isolates Americans and creates confusion in international contexts.

The precision argument is overrated. Do you really need to distinguish between 72°F and 73°F? Most people can't even sense a one-degree Fahrenheit difference. And if you need precision, Celsius allows decimals.

Negative numbers aren't that scary. Canadians, Scandinavians, and Russians handle negative Celsius temperatures just fine.

The Bottom Line

Fahrenheit and Celsius are two different ways of measuring the same thing, created about 18 years apart by two scientists with different goals. Fahrenheit wanted precision and easy division of degrees. Celsius wanted simplicity and logical reference points.

Both systems work. Both have advantages and disadvantages. The main difference now is that one is used by almost everyone, and the other is used almost exclusively by Americans.

Will the U.S. ever switch? Probably not anytime soon. The 1975 attempt failed, and there's even less political will to try again now. Most Americans are comfortable with Fahrenheit, the cost of changing everything would be enormous, and there's no crisis forcing the issue.

So for the foreseeable future, Americans will keep saying "it's 75 degrees and sunny" while the rest of the world says "it's 24 degrees and sunny," and both will be describing the exact same pleasant day.

Just remember: when you travel, bring a conversion chart. Or at least remember that -40 is the same in both systems, though hopefully you'll never experience weather that cold.

Sources

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HowStuffWorks. (2021). Why Does the U.S. Use Fahrenheit Instead of Celsius? Retrieved from https://science.howstuffworks.com/nature/climate-weather/atmospheric/us-use-fahrenheit.htm

EarthDate. The Fahrenheit Few. Retrieved from https://www.earthdate.org/episodes/the-fahrenheit-few

American Physical Society. (2022). May 24, 1686: Daniel Gabriel Fahrenheit and the Birth of Precision Thermometry. Retrieved from https://www.aps.org/apsnews/2022/05/fahrenheit-birth-precision-thermometry

Spectrum News. (2023). The change to Celsius in U.S. remains stalled; here's why. Retrieved from https://spectrumlocalnews.com/mo/st-louis/weather/2023/02/20/the-change-to-celsius-in-u-s--remains-stalled--here-s-why

New World Encyclopedia. Fahrenheit. Retrieved from https://www.newworldencyclopedia.org/entry/Fahrenheit

WHAS11. Celsius vs. Fahrenheit: A brief history of temperature. Retrieved from https://www.whas11.com/article/weather/weather-smarts/celsius-fahrenheit-covid-vaccine-brief-history-of-temperature/417-e26d6164-c164-4ff8-bd00-1dc08e99e841