Kalkulo

Temperature converter

Convert Celsius, Fahrenheit and Kelvin. UK weather uses Celsius but ovens and older recipes often use Fahrenheit; °F = °C x 1.8 + 32.

About this tool

Why use this tool

The UK uses Celsius for weather (Met Office) and cooking, but many older cookbooks and imported American recipes use Fahrenheit; science uses Kelvin. Converting matters for oven settings on inherited or imported appliances, reading US recipes, tracking body temperature with older UK thermometers still marked in Fahrenheit, and understanding NHS clinical scales. Britain switched daily weather forecasts to Celsius in 1962; medicine went metric in the 1970s.

How it works

°C = (°F − 32) × 5/9. °F = °C × 9/5 + 32. K = °C + 273.15. Water freezes at 0°C (32°F, 273.15 K) and boils at 100°C (212°F, 373.15 K) at sea level. Body temperature 37°C = 98.6°F. NHS fever threshold: 38°C (100.4°F) in adults; 38°C in babies under 3 months requires urgent care per NICE guidance.

Real example

A hot British summer day at 30°C = 86°F. Fan oven at 180°C = 356°F conventional. A cold snap at −5°C = 23°F. NHS classifies hypothermia below 35°C (95°F). Standard UK room temperature target: 18–21°C (64–70°F) per NHS winter guidance for older adults.

Practical tips

Quick mental math: °C × 2 + 30 ≈ °F (25°C ≈ 80°F). Kitchen shortcuts: Gas Mark 4 = 180°C = 356°F; Gas Mark 6 = 200°C = 400°F; Gas Mark 7 = 220°C = 425°F. Fan ovens run 20°C hotter than conventional — subtract 20 for fan setting. NHS 111 escalation temperatures: 38°C+ in babies under 3 months, 39°C+ in babies 3–6 months. Set your Met Office app to Celsius (default). Energy Saving Trust recommends heating at 18°C in bedrooms and 21°C in living rooms.

Disclaimer

Conversions follow the NPL (National Physical Laboratory) SI standards. Domestic thermometers have accuracy of ±0.3°C to ±2°C. For clinical or laboratory use, choose UKAS-calibrated instruments. NHS temperature thresholds change with age; consult NHS 111 or your GP for medical advice.

Frequently asked questions

Does the UK use Celsius or Fahrenheit?⌄
The UK uses Celsius for weather forecasts and almost all everyday purposes. Fahrenheit still appears on older thermostats, some recipes and in headlines during heatwaves, so being able to convert both ways is useful. Ovens are usually marked in Celsius, sometimes alongside gas marks.
How do gas marks convert to Celsius and Fahrenheit?⌄
Gas mark 1 is about 140 C (275 F), gas mark 4 is about 180 C (350 F), gas mark 6 is about 200 C (400 F) and gas mark 9 is about 240 C (475 F). Each gas mark step is roughly 14 C (25 F).
What counts as a fever?⌄
The NHS defines a high temperature as 38 C (100.4 F) or above. Normal body temperature is around 37 C (98.6 F) but varies between people and through the day.Source: NHS
Can a Kelvin temperature be negative?⌄
No. 0 Kelvin is absolute zero, equal to -273.15 C, the coldest anything can theoretically get. Kelvin values are always zero or positive, whereas Celsius and Fahrenheit readings are often negative in winter.
Why is there a 273.15 in the Kelvin conversion?⌄
One Kelvin is exactly the same size as one degree Celsius, so only the starting point differs: Celsius puts zero at the freezing point of water, Kelvin puts it at absolute zero, 273.15 degrees lower. So K = C + 273.15.

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