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 (since 1965) | — |
| 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 had two serious metrication efforts — Metric Act 1975 and the United States Metric Board (1975-1982). Both 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. UK law requires Celsius for weather and scientific use. Fahrenheit is understood but not standard in the UK.