Temperature Converter

Celsius Temperature Scale Explained (°C)

Celsius (°C) is the most commonly used temperature scale worldwide. It was introduced in the 18th century by Swedish scientist Anders Celsius and is designed to be simple and practical.

What makes Celsius easy to understand is its clear water-based reference points:

0°C = water freezes

100°C = water boils (at standard air pressure)

Because these points are familiar and consistent, Celsius is used every day for weather reports, cooking, health readings, and science. You may also hear it called the centigrade scale.

Fahrenheit Temperature Scale (°F)

Fahrenheit (°F) is a temperature scale created by Daniel Gabriel Fahrenheit, who also helped popularize the mercury-in-glass thermometer for more consistent and accurate readings.

To build a reliable scale, Fahrenheit chose fixed reference points that could be repeated:

• 0°F was based on a very cold brine mixture (ice and salt).
• He also used human body temperature as a reference point for the upper end of the scale.

Today, Fahrenheit is used most often in the United States and a few other places—especially for weather, cooking, and daily temperature readings. If you need to switch between °F and °C, our temperature converter calculates it instantly (and shows the formula if you want to do it by hand).

Kelvin Temperature Scale: The Absolute Standard for Measuring Heat

Kelvin (K) is the SI base unit of temperature and the absolute temperature scale used in science and engineering. It starts at absolute zero (0 K)—the point where thermal energy is at its minimum and particle motion is as low as physically possible.

The scale is named after William Thomson (Lord Kelvin), who helped shape the idea of measuring temperature from a true zero point rather than using water-based reference points. Because Kelvin is tied to fundamental physics, it works the same in every lab, every country, and every industry—making it essential for thermodynamics, chemistry, physics, space science, weather research, and engineering.

A key detail: Kelvin doesn’t use the degree symbol. You write 300 K, not 300°K.

And the scale steps match Celsius: 1 K = 1°C change, but Kelvin’s starting point is different.

What Is the Rankine Scale? Simple Guide to °R (Absolute Fahrenheit)

The Rankine scale (°R) is an absolute temperature scale used in some engineering and science work. It was created in the 1800s by William John Macquorn Rankine, a Scottish engineer and physicist.

Why Rankine matters

Rankine starts at absolute zero. Absolute zero is the coldest possible temperature. At this point, heat energy is at its minimum.

That’s why Rankine is helpful in thermodynamics, where engineers often must use an absolute temperature scale.

Key facts

• 0°R = absolute zero
• 0°R = −459.67°F
• The size of 1°R is the same as 1°F
• (So Rankine increases in the same step size as Fahrenheit.)

Where Rankine is used today

You may see °R in technical fields that use Fahrenheit-based calculations, such as:

• Heat transfer
• Fluid dynamics
• Energy and power systems
• Thermodynamic formulas in engineering

Rankine vs Kelvin

Rankine is like Kelvin, but with Fahrenheit-sized degrees:

• Kelvin (K) uses Celsius-sized steps
• Rankine (°R) uses Fahrenheit-sized steps
• Both scales start at absolute zero, which makes them “absolute” scales.

If you work with engineering formulas that need absolute temperature and you’re using Fahrenheit values, Rankine is the clean, correct option.