Temperature Converter

Multiply the Celsius value by 9/5 (or 1.8) and add 32. Formula: °F = (°C × 9/5) + 32. Example: 100°C = (100 × 1.8) + 32 = 212°F. To convert the other way: °C = (°F − 32) × 5/9. Example: 98.6°F = (98.6 − 32) × 5/9 = 37°C.

Simply add 273.15. Formula: K = °C + 273.15. The Kelvin scale has the same interval size as Celsius — a change of 1°C is a change of 1 K. The only difference is the starting point: 0 K is absolute zero (−273.15°C). Water freezes at 273.15 K and boils at 373.15 K.

The Celsius and Fahrenheit scales cross at exactly −40°. At −40, both scales give the same number: −40°C = −40°F. This is because the formula °F = (°C × 1.8) + 32 has a solution at −40. Below −40, the Fahrenheit value is lower; above −40, the Fahrenheit value is higher than the Celsius value.

Absolute zero is the coldest theoretically possible temperature, at which all molecular motion stops. It is defined as 0 Kelvin = −273.15°C = −459.67°F = 0°R. It has never been reached in practice, only approached to within a few billionths of a Kelvin. The Kelvin and Rankine scales both start at absolute zero, which is why they have no negative values.

The commonly cited value is 37°C (98.6°F), established in 1851 by Carl Wunderlich. Modern studies suggest the average is slightly lower at 36.6°C (97.9°F), and varies by time of day, age and measurement location. A fever is typically defined as 38°C (100.4°F) or above. The normal range is roughly 36.1–37.2°C (97–99°F).

Both Kelvin and Rankine start at absolute zero, making them absolute temperature scales. The difference is the size of the degree interval. Kelvin uses the same interval as Celsius (metric system), while Rankine uses the same interval as Fahrenheit (imperial system). So 1 K = 1.8°R. Rankine is mostly used in some US engineering fields. Conversion: °R = K × 1.8 = °F + 459.67.

The Fahrenheit scale was established in 1724 by Daniel Fahrenheit and adopted widely before the metric system was standardized. The US, along with the Cayman Islands and a few other territories, never switched to Celsius. The UK officially adopted Celsius in the 1960s-70s but still uses Fahrenheit colloquially for weather. The Celsius scale, proposed in 1742 by Anders Celsius, is used in every other country and in all scientific contexts worldwide.

At standard atmospheric pressure (1 atm = 101.325 kPa), water freezes at 0°C (32°F, 273.15 K) and boils at 100°C (212°F, 373.15 K). These were actually the original definition of the Celsius scale. At higher altitudes the boiling point drops (e.g. water boils at ~90°C at 3,000 m elevation). At higher pressures the boiling point rises — this is why pressure cookers cook faster.

37°C = 98.6°F. This is the standard human body temperature. Calculation: (37 × 9/5) + 32 = 66.6 + 32 = 98.6. Other useful medical temperatures: 36°C = 96.8°F, 38°C = 100.4°F (fever threshold), 39°C = 102.2°F, 40°C = 104°F (high fever). Use this converter to check any temperature quickly.

180°C = 356°F, which rounds to 350°F in most recipes — a moderate oven. Other common oven conversions: 160°C = 320°F (slow/low) · 200°C = 392°F (hot) · 220°C = 428°F (very hot) · 250°C = 482°F (extremely hot). UK recipes often use Gas Mark: 180°C = Gas Mark 4. Fan ovens typically run 20°C lower than conventional ovens.