Temperature Converter — Convert °C, °F, K, °R & More

About the Temperature Converter

Temperature is the one measurement where the different unit systems don't just use a different scale factor — they start counting from a different zero. A weather forecast in Fahrenheit, a lab reading in Kelvin, a thermodynamics textbook in Rankine: this tool lets you enter a value once and see it converted to every common temperature scale at the same time.

How to Use This Tool

Enter the temperature value you want to convert.
Select the scale that value is currently in.
The table updates automatically, showing the equivalent value on every other scale.

Values below absolute zero (−273.15 °C) are rejected, since no temperature scale can go lower than that physical limit.

Conversion Formulas

Unlike energy, length or mass, temperature scales are not simple multiples of each other — each one has its own offset. Celsius is used as the common bridge:

°F = °C × 9/5 + 32 K = °C + 273.15 °R = (°C + 273.15) × 9/5 °Ré = °C × 4/5

To go the other way (from any scale back to Celsius), each formula is simply solved in reverse.

Temperature Scale Reference

Scale	Symbol	Water Freezes	Water Boils	Absolute Zero
Celsius	°C	0 °C	100 °C	−273.15 °C
Fahrenheit	°F	32 °F	212 °F	−459.67 °F
Kelvin	K	273.15 K	373.15 K	0 K
Rankine	°R	491.67 °R	671.67 °R	0 °R
Réaumur	°Ré	0 °Ré	80 °Ré	−218.52 °Ré

Note: Kelvin and Rankine are absolute scales (their zero point is absolute zero), while Celsius, Fahrenheit and Réaumur are relative scales anchored to the freezing point of water.

Worked Examples

Example 1 — Celsius to Fahrenheit

A pleasant 25 °C day: 25 × 9/5 + 32 = 77 °F.

Example 2 — Fahrenheit to Celsius

Body temperature at 98.6 °F: (98.6 − 32) × 5/9 = 37 °C.

Example 3 — Celsius to Kelvin

Room temperature at 20 °C: 20 + 273.15 = 293.15 K.

Example 4 — Kelvin to Rankine

A cryogenic system at 77 K (liquid nitrogen boiling point): (77 − 273.15 + 273.15) × 9/5 = 138.6 °R.

Frequently Asked Questions

What is absolute zero, and why can't I enter a lower value?

Absolute zero (−273.15 °C, 0 K, −459.67 °F) is the coldest temperature theoretically possible — the point where particles have minimal thermal motion. No real or converted temperature can go below it, so this tool blocks values under that limit in whichever unit you enter.

How do I convert Celsius to Fahrenheit?

Multiply by 9/5 (or 1.8) and add 32: °F = °C × 9/5 + 32. To go back, subtract 32 first and multiply by 5/9.

What's the difference between Kelvin and Celsius?

They use the same size of degree — a 1 K change equals a 1 °C change — but Kelvin starts at absolute zero instead of the freezing point of water. K = °C + 273.15.

What is the Rankine scale used for?

Rankine is an absolute scale (like Kelvin) but sized in Fahrenheit-sized degrees. It shows up in US thermodynamics and engineering formulas that need an absolute temperature but are otherwise working in imperial units.

Is the Réaumur scale still used?

Rarely today — it was common in parts of Europe until the 20th century, and still appears occasionally in some traditional cheese and jam-making recipes. Water freezes at 0 °Ré and boils at 80 °Ré.