Free Temperature Converter

Temperature Converter: Switch Between Every Temperature Scale

This free Temperature Converter translates a single reading across Celsius, Fahrenheit, Kelvin, and several historical scales in one click. Whether you need a quick Celsius to Fahrenheit result for a recipe or a precise Fahrenheit to Celsius reading for a lab report, the tool removes the mental arithmetic — and the mistakes that come with it.

What Temperature Really Measures

Temperature looks simple on a thermometer but is surprisingly subtle to define. In physics, temperature reflects the average kinetic energy of the particles in a substance: the hotter something is, the faster its atoms and molecules vibrate. Heat, in this view, is energy in transit, flowing from a hotter body to a cooler one. This is why friction always produces warmth — it converts kinetic energy into particle motion.

Temperature also threads through many other physical relationships. Pressure, volume, and temperature link together through the ideal gas law, which is why a hot tire reads higher pressure and why warm air is less dense (and less buoyant) than cold air.

The Celsius Scale

Anders Celsius built his scale on two easily reproducible anchors: the freezing and boiling points of pure water at one atmosphere of pressure, set at $0\ ^{\circ}\text{C}$ and $100\ ^{\circ}\text{C}$. The hundred equal divisions between them give the scale its alternate name — centigrade. Celsius assigns friendly numbers to everyday conditions, which is why most of the world uses it for weather, cooking, and clinical readings.

The Kelvin Scale

Kelvin is the SI unit of temperature and the backbone of scientific work. Its zero point is absolute zero, the theoretical lower limit at which particle motion nearly stops:

$$0\ \text{K} = -273.15\ ^{\circ}\text{C} = -459.67\ ^{\circ}\text{F}$$

A kelvin is the same size as a Celsius degree, so the scales differ only in their starting point. Water freezes at $273.15\ \text{K}$ and boils at $373.15\ \text{K}$. Kelvin never goes negative in everyday use, which keeps scientific calculations clean.

The Fahrenheit Scale

Daniel Gabriel Fahrenheit designed his scale around brine and approximate body temperature, landing water's freezing point at $32\ ^{\circ}\text{F}$ and its boiling point at $212\ ^{\circ}\text{F}$. The scale dominates everyday life in the United States, so anyone reading American weather, recipes, or oven dials needs reliable C to F and F to C conversions.

The Core Conversion Formulas

To move between the three main scales, use these relationships. For Celsius to Fahrenheit:

$$T_{\text{F}} = T_{\text{C}} \times \frac{9}{5} + 32$$

For Fahrenheit to Celsius:

$$T_{\text{C}} = (T_{\text{F}} - 32) \times \frac{5}{9}$$

And between Celsius and Kelvin:

$$T_{\text{K}} = T_{\text{C}} + 273.15$$

A handy shortcut for a rough C to F estimate: double the Celsius value and add 30. This stays within a few degrees for typical weather-range temperatures.

Lesser-Known Scales

Beyond the big three, this converter also handles Rankine, Delisle, Newton, Reaumur, and Romer — scales invented by scientists whose names they carry. Most are historical curiosities today, but they still appear in old engineering tables and specialized literature.

How to Use the Converter

1. Type the temperature value into any unit field.
2. Every other field updates instantly with the converted reading.
3. Use the checkboxes to show or hide the scales you care about.

No formula, no scratchpad — just enter a number and read every equivalent at once.