Temperature Converter

To convert Celsius to Fahrenheit, multiply by 9/5 (1.8) and then add 32. Formula: °F = (°C × 9/5) + 32. For example, 20°C = (20 × 1.8) + 32 = 36 + 32 = 68°F. A quick mental estimate: double the Celsius value and add 30 (e.g., 20°C → 40 + 30 = 70°F, close enough for everyday use).

Kelvin is the SI base unit for temperature. Unlike Celsius and Fahrenheit, Kelvin starts at absolute zero — the lowest theoretically possible temperature — and has no negative values. The scale size is identical to Celsius: a 1 K change equals a 1°C change. To convert Celsius to Kelvin, simply add 273.15. Water freezes at 273.15 K and boils at 373.15 K.

Normal human body temperature is 98.6°F (37°C or 310.15 K). However, body temperature can vary between 97°F (36.1°C) and 99°F (37.2°C) and still be considered normal. A fever is generally defined as a temperature above 100.4°F (38°C).

Absolute zero is the lowest possible temperature, where all thermal motion of atoms and molecules ceases. It is defined as exactly 0 K, which equals −273.15°C or −459.67°F. Nothing in the universe can reach absolute zero, though scientists have come within billionths of a degree in laboratory conditions.

Rankine is a thermodynamic temperature scale used mainly in engineering in the United States. Like Kelvin, it starts at absolute zero (0°Ra), but uses Fahrenheit-sized degrees. The relationship is: °Ra = °F + 459.67. Water freezes at 491.67°Ra and boils at 671.67°Ra.