Why Does America Use Fahrenheit?
Why does US use Fahrenheit when almost every other country reports the weather in Celsius? Because Fahrenheit got there first, and America never passed a law to remove it. The scale is three centuries old, older than the United States itself, and it survived for the most ordinary reason a measurement survives: everyone already knew what 70 degrees felt like.
A scale built from brine and blood
Fahrenheit built his scale around three fixed points he could reproduce in a workshop: 0 °F was the coldest temperature his brine of ice, water and ammonium chloride could reach; 32 °F was water freezing; and 96 °F was, approximately, human body temperature. The numbers look arbitrary today because they were chosen for the instrument maker, not the mathematician — Celsius, devised decades later by Anders Celsius, chose the cleaner 0 °C for freezing and 100 °C for boiling, which is why it spread with the metric system. But by the time Celsius caught on, Britain and its colonies were already thoroughly Fahrenheit, and the young United States inherited the scale with everything else.
The switch that never came
Britain itself eventually metricated much of daily life, but the US took a different path: the Metric Conversion Act of 1975 declared metric the preferred system yet made conversion voluntary, with no deadline and no penalties. Industry converted where it paid — cars, pharmaceuticals, science — and everyday life did not. Replacing Fahrenheit would mean reprinting every cookbook, reprogramming every thermostat, re-teaching every weather viewer what "hot" means, and accepting years of confusion, all to arrive at numbers that carry no practical advantage for weather or cooking. No administration has found that bargain worth making.
The anchors worth memorising
| Point | Fahrenheit | Celsius |
|---|
| Water freezes | 32 °F | 0 °C |
| Room temperature | 68–72 °F | 20–22 °C |
| Body temperature | 98.6 °F | 37 °C |
| Water boils | 212 °F | 100 °C |
| Scales agree | −40 °F | −40 °C |
For exact conversions, use the Fahrenheit to Celsius converter, and for the other half of the American measurement story see metric vs imperial, side by side.
Frequently asked questions
Why does the US use Fahrenheit instead of Celsius?
Fahrenheit was the established scale in the English-speaking world before Celsius spread, and the US never made metrication compulsory. The 1975 Metric Conversion Act made metric use voluntary, so everyday life — weather, cooking, thermostats — stayed Fahrenheit while science and medicine went Celsius.
Who invented Fahrenheit?
Daniel Gabriel Fahrenheit, a Polish-Dutch instrument maker, who published the scale in 1714. He set 0 °F with a freezing brine mixture, 32 °F at the freezing point of water, and originally 96 °F for body temperature — later refined to 98.6 °F.
Is Fahrenheit more precise than Celsius?
Not inherently — both scales can carry decimals. Fahrenheit's smaller degrees (one Celsius degree equals 1.8 Fahrenheit degrees) give whole-number readings that feel more granular for weather: 72 °F versus 22 °C is the same temperature, just a finer-looking number.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9: °C = (°F − 32) × 5/9. To go the other way, multiply by 9/5 and add 32: °F = °C × 9/5 + 32. So 68 °F = 20 °C, and −40 is the one temperature where both scales agree.
Does any other country use Fahrenheit?
Only a handful: the US, Liberia and a few island territories use it officially for everyday weather. Everywhere else uses Celsius for daily life, though Fahrenheit still appears in some specialised US-influenced industries worldwide.