Why Does the US Use Fahrenheit? A Short History
Fahrenheit was invented in 1724 and stuck in the US while most of the world moved to Celsius. Learn the history and the exact relationship between the two scales.
Fahrenheit Came First
The Fahrenheit scale was introduced by Daniel Gabriel Fahrenheit, a Polish-German physicist, in 1724. He set 32°F as the freezing point of water and 212°F as the boiling point, with 180 degrees between them. The scale was widely adopted in the English-speaking world, including the American colonies, long before Celsius appeared.
Anders Celsius proposed his scale in 1742, originally inverted (0 for boiling, 100 for freezing) before it was flipped to the modern form: 0°C freezes and 100°C boils. Celsius is now the metric-world standard, but the US had already standardized on Fahrenheit in daily life.
Why the US Kept Fahrenheit
When the US considered metric adoption, temperature was a visible, everyday habit. Fahrenheit divides the human-comfortable range into many small steps (roughly 0°F to 100°F for cold to hot weather), which some find intuitive for weather. Combined with the voluntary nature of US metric conversion, Fahrenheit simply persisted in forecasts, thermostats, and ovens.
The Two Scales Today
Most countries use Celsius for everything. The US uses Fahrenheit for weather and cooking but Celsius in science and medicine. The coexistence is the same pattern seen across US measurement: customary at home, metric in technical work.
Converting Between Them
The exact formulas are Celsius = (Fahrenheit - 32) x 5/9 and Fahrenheit = (Celsius x 9/5) + 32. Our Celsius to Fahrenheit converter does either direction instantly. For the reverse view, see our Fahrenheit to Celsius guide.
Useful Anchor Points
Water freezes at 32°F / 0°C and boils at 212°F / 100°C. Room temperature is about 68°F / 20°C. Normal body temperature is 98.6°F / 37°C. These anchors make it easy to picture one scale in terms of the other.
Frequently Asked Questions
Who invented the Fahrenheit scale?
Daniel Gabriel Fahrenheit, a Polish-German physicist, introduced it in 1724.
Why did the US not switch to Celsius?
US metric conversion was voluntary, and Fahrenheit was already the everyday standard for weather and cooking, so it persisted.
What is the formula to convert Fahrenheit to Celsius?
Celsius = (Fahrenheit - 32) x 5/9. For example, (212 - 32) x 5/9 = 100°C.
Is Celsius used in the US at all?
Yes, in science, medicine, and many technical fields. Everyday weather and oven temperatures are usually Fahrenheit.
What are the key anchor temperatures?
Water freezes at 32°F / 0°C and boils at 212°F / 100°C; normal body temperature is 98.6°F / 37°C.
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Quick Summary
The US uses Fahrenheit because the scale predates Celsius and became the everyday standard before metric adoption, which remained voluntary. The two scales convert exactly: Fahrenheit = (Celsius x 9/5) + 32, and Celsius = (Fahrenheit - 32) x 5/9.
Related Guide
Fahrenheit to Celsius
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT°F = °C × 9/5 + 32 (exact linear relation)
- EXACT°C = (°F − 32) × 5/9 (exact inverse relation)
- EXACTKelvin (K) = °C + 273.15 (exact offset)
- EXACTWater freezes at 0 °C = 32 °F and boils at 100 °C = 212 °F
Common Pitfalls & How to Avoid Them
Subtract 32 BEFORE multiplying
°C = (°F − 32) × 5/9. Doing 5/9 × °F − 32 instead gives a wrong answer because the offset must be removed first. Parentheses matter.
Degrees are not the same size
A 1 °C step equals a 1.8 °F step. A "10-degree" forecast difference is 18 °F, not 10 °F. This is why a 5 °C day feels very different from a 15 °C day.
Negative signs
Below freezing, (°F − 32) is negative; keep the sign through the whole calculation. −40 °C = −40 °F is the only point where the two scales meet.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST — SI Units: Temperature
Last Updated 2026 | This article was reviewed for accuracy