Temperature Converter

The UK officially uses Celsius for temperature measurement, but Fahrenheit is still commonly understood, especially among older generations and in weather discussions. This converter handles Celsius, Fahrenheit and Kelvin in both directions, working from the standard formulas: °F = (°C × 9/5) + 32 going one way, and °C = (°F − 32) × 5/9 coming back. Britain switched officially in 1972, yet forecasters still reach for the older scale when they want emphasis, as in 'a sweltering 90°F!'.

A handful of anchor points make mental conversion much easier. Water freezes at 0°C (32°F) and boils at 100°C (212°F) at sea level. Room temperature of 20°C is 68°F, a cool British day of 16°C is 60.8°F, 25°C is 77°F, and a genuinely hot 30°C is 86°F. Normal body temperature sits close to 37°C (98.6°F). The two scales cross at exactly one value, −40°C, which is also −40°F.

Kelvin is the scientific scale and takes no degree symbol. Convert with K = °C + 273.15, so absolute zero, the theoretical lower limit that has never been achieved, is −273.15°C or 0 K. Water freezes at 273.15 K, body temperature is around 310 K, and water boils at 373.15 K. A kelvin is the same size as a degree Celsius, so only the starting point moves. University physics uses Kelvin for thermodynamics while daily life stays with Celsius, and the same scale describes the colour of light, from a warm white bulb at 2700K to a daylight bulb at 6500K, with the sun at 5778K.

UK weather records show how narrow the national spread really is. The highest reading was 40.3°C (104.5°F) at Coningsby in Lincolnshire on 19 July 2022, the first UK day above 40°C. The lowest was −27.2°C (−17.0°F), recorded at Braemar and Altnaharra in Scotland. An average summer day falls between 16-22°C and an average winter day between 3-8°C. London runs 1.5-2°C warmer than the countryside around it thanks to the urban heat island, while Scotland is 2-4°C cooler than southern England. The country has warmed by about 1.0°C since 1980, and the 10 hottest UK years on record have all occurred since 2002.

Body temperature is where a fraction of a degree changes the advice. A normal reading falls between 36.1-37.2°C (97-99°F). The NHS treats 38.0°C (100.4°F) and above as a fever, 39.5°C (103.1°F) and above as a high fever, and anything past 40°C (104°F) as heatstroke needing emergency care. At the other end, below 35°C (95°F) is hypothermia, and below 32°C is severe. Your own reading drifts through the day, lowest around 4am and highest around 6pm, a swing of roughly 0.5°C. Women's basal temperature rises 0.3-0.5°C after ovulation, and children typically run 0.3-0.5°C warmer than adults. An oral reading is usually 0.5°C below rectal, and an armpit reading about 1°C below.

British ovens still carry gas marks alongside degrees. Gas Mark 1 is 140°C or 275°F, Gas 4 is 180°C or 350°F and covers most baking, Gas 6 is 200°C or 400°F, and Gas 9 is 240°C or 475°F for pizza and anything wanting fierce heat. A fan-assisted oven runs 20°C hotter at the same dial setting, so drop a conventional recipe by 20°C, taking 180°C down to 160°C fan. Sugar work demands its own precision, with soft ball at 116°C (240°F), hard crack at 149°C (300°F) and caramel at 170°C (340°F).

Meat is judged by internal temperature rather than by time in the oven. Rare is 52°C (125°F), medium-rare 57°C (135°F), medium 63°C (145°F), and well done 71°C (160°F) or above. Food safety works from the same probe. Hot food should be held above 63°C and cold food below 5°C, since 5-63°C is the danger zone in which bacteria multiply fastest. The overlap is worth spotting: 63°C is both the target for a medium steak and the minimum holding temperature for a hot buffet.