Why the UK uses Celsius vs Why the US uses Fahrenheit
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
UK formal contexts, science, weather, medicine, EU markets.
US everyday use, body temperature (98.6°F), weather, cooking (especially ovens in older US recipes).
| Aspect | Why the UK uses Celsius | Why the US uses Fahrenheit |
|---|---|---|
| UK official standard | Celsius (official and scientific use) | — |
| UK informal use | Both — older generation often uses °F | — |
| US standard | Fahrenheit | — |
| Scientific standard worldwide | Kelvin / Celsius | — |
| Body temperature convention | 37°C (UK/EU medicine) | 98.6°F (US) |
Frequently asked
Why hasn't the US switched to Celsius?
The US made a serious but voluntary metrication effort — the Metric Conversion Act 1975 and the United States Metric Board (1975-1982). It failed due to public resistance and lack of legal mandate. Without a requirement, the cost of switching road signs, tools, recipes and cultural norms has never been politically viable.
When is Fahrenheit still used in the UK?
Body temperature (some people still say '98.6' for normal), very old recipes, some older people for weather. Celsius is the standard for weather and science in the UK. Fahrenheit is understood but not standard.
Frequently asked questions
Why hasn't the US switched to Celsius?
The US made a serious but voluntary metrication effort — the Metric Conversion Act 1975 and the United States Metric Board (1975-1982). It failed due to public resistance and lack of legal mandate. Without a requirement, the cost of switching road signs, tools, recipes and cultural norms has never been politically viable.
When is Fahrenheit still used in the UK?
Body temperature (some people still say '98.6' for normal), very old recipes, some older people for weather. Celsius is the standard for weather and science in the UK. Fahrenheit is understood but not standard.