Temperature Converter – Celsius, Fahrenheit, Kelvin & More

Q: What is absolute zero?

Absolute zero is 0 Kelvin = −273.15°C = −459.67°F. The lowest possible temperature where all molecular motion stops.

Q: Is this Temperature Converter free?

Yes, completely free with no signup required.

Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, Rankine and Réaumur instantly. See all conversions at once.

Enter Temperature

ValueFrom

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100 °C in all units

🌡️ Celsius (°C)100 °C

🌡️ Fahrenheit (°F) ← selected212 °F

🔬 Kelvin (K)373.15 K

🔬 Rankine (°R)671.67 °R

📜 Réaumur (°Ré)80 °Ré

Temperature Conversion Made Easy

Our Free Temperature Converter supports all 5 major temperature scales — Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Whether you are a student solving a physics problem, a chef adjusting oven settings, or a scientist working with absolute temperatures, get instant and accurate results.

Unlike simple unit converters, temperature scales cannot be converted with a single multiplication factor. Each scale has its own zero point and step size. Our calculator uses the correct formulas for every conversion automatically.

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5 Scales

Celsius, Fahrenheit, Kelvin, Rankine and Réaumur — all major temperature scales in one tool.

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All at Once

See your value converted to all 5 scales simultaneously in the quick reference panel.

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Scientifically Accurate

Uses exact formulas — not approximations. Results are accurate to 6 decimal places.

Temperature Conversion Formulas

The exact math behind every conversion

Core Formulas

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

All formulas via Celsius as baseKelvin has no negative values

Common Temperature Reference Points

Reference Point	°C	°F	K	°R
Absolute Zero	-273.15	-459.67	0	0
Water Freezes	0	32	273.15	491.67
Room Temperature	22	71.6	295.15	531.27
Body Temperature	37	98.6	310.15	558.27
Water Boils	100	212	373.15	671.67
Oven (Baking)	180	356	453.15	815.67
Iron Melts	1538	2800.4	1811.15	3260.07
Sun Surface	5505	9941	5778.15	10400.67

Understanding Temperature Scales

🌡️ Celsius (°C)

The most widely used temperature scale worldwide. Water freezes at 0°C and boils at 100°C at standard pressure. Used in all countries except the United States for everyday temperature measurement.

🌡️ Fahrenheit (°F)

Primarily used in the United States. Water freezes at 32°F and boils at 212°F. Body temperature is 98.6°F. Developed by Daniel Gabriel Fahrenheit in 1724.

🔬 Kelvin (K)

The SI base unit of temperature used in science and engineering. Starts at absolute zero (0 K = −273.15°C) — the coldest possible temperature. Has no negative values. Used in physics, chemistry, and astronomy.

🔬 Rankine (°R)

Used in some engineering fields in the United States. Like Kelvin, it starts at absolute zero, but uses Fahrenheit-sized degrees. 0°R = 0 K = −273.15°C.

📜 Réaumur (°Ré)

A historical temperature scale where water freezes at 0°Ré and boils at 80°Ré. No longer in common use but still referenced in old scientific literature and some food industries.

❄️ Absolute Zero

The lowest possible temperature — −273.15°C, −459.67°F, or 0 K. At absolute zero, all molecular motion stops. It is a theoretical limit that cannot be physically reached.

Common Use Cases

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Cooking & Baking

Convert oven temperatures between Celsius and Fahrenheit when following international recipes.

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Science & Lab

Convert between Kelvin and Celsius for chemistry experiments, thermodynamics, and physics problems.

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Travel

Understand weather forecasts in Fahrenheit when visiting the US, or Celsius when in Europe.

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Medical

Convert body temperature readings between Celsius and Fahrenheit for international medical records.

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Weather

Check if -10°C is colder than 20°F when comparing international weather forecasts.

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Engineering

Convert between Rankine and Kelvin for thermodynamic calculations in mechanical engineering.

Temperature Converter FAQ

How do I convert Celsius to Fahrenheit?

Multiply by 9/5 then add 32. Formula: °F = (°C × 9/5) + 32. For example, 100°C = 212°F. Our calculator does this automatically.

What is absolute zero?

Absolute zero is the lowest possible temperature — 0 Kelvin, which equals −273.15°C or −459.67°F. At this point all molecular motion theoretically stops.

Why can Kelvin not be negative?

Because Kelvin starts at absolute zero — the coldest possible temperature. There is nothing colder than 0 K, so negative Kelvin values do not exist physically.

What is normal body temperature in Fahrenheit?

Normal body temperature is 37°C = 98.6°F. A fever is generally considered above 38°C (100.4°F).

What is the difference between Kelvin and Rankine?

Both start at absolute zero, but Kelvin uses Celsius-sized degrees while Rankine uses Fahrenheit-sized degrees. 0 K = 0°R, but 1 K = 1.8°R.

Is this Temperature Converter free?

Yes, completely free with no signup or registration required.