Temperature Converter Fast & accurate conversions
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Temperature Converter

Instantly convert between Celsius, Fahrenheit, Kelvin, Rankine & Réaumur — with step-by-step working.

5 Scales Step-by-step Working No Sign-up
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Key Reference Points
Boiling Point (Water)
100 °C · 212 °F
373.15 K · 80 °Ré
Freezing Point (Water)
0 °C · 32 °F
273.15 K · 0 °Ré
Absolute Zero
−273.15 °C · −459.67 °F
0 K · 0 °R
Conversion Formulas
FromToFormula
CelsiusFahrenheit°F = °C × 9/5 + 32
CelsiusKelvinK = °C + 273.15
CelsiusRankine°R = °C × 9/5 + 491.67
CelsiusRéaumur°Ré = °C × 4/5
FahrenheitCelsius°C = (°F − 32) × 5/9
FahrenheitKelvinK = (°F + 459.67) × 5/9
FahrenheitRankine°R = °F + 459.67
FahrenheitRéaumur°Ré = (°F − 32) × 4/9
KelvinCelsius°C = K − 273.15
KelvinFahrenheit°F = K × 9/5 − 459.67
KelvinRankine°R = K × 9/5
KelvinRéaumur°Ré = (K − 273.15) × 4/5
RankineCelsius°C = (°R − 491.67) × 5/9
RankineFahrenheit°F = °R − 459.67
RankineKelvinK = °R × 5/9
RéaumurCelsius°C = °Ré × 5/4
RéaumurFahrenheit°F = °Ré × 9/4 + 32
RéaumurKelvinK = °Ré × 5/4 + 273.15
Conversion Chart

How to Use This Temperature Converter

Get an accurate result in seconds — no account, no ads. The tool also shows full step-by-step working so you can verify or learn the calculation.

1

Select your scales

Choose the scale to convert from and the scale to convert to — Celsius, Fahrenheit, Kelvin, Rankine, or Réaumur.

2

Type your value

Enter any number — positive, negative, or decimal. The result appears instantly as you type. No button press needed.

3

Check the working

The Step-by-step working box shows the exact formula and calculation — useful for homework, exams, or verification.

Popular Temperature Converters

Need a dedicated converter for a specific pair? Each page below includes a focused tool, detailed formulas, common conversion tables, and real-world examples.

°C → °F

Celsius to Fahrenheit Converter

The most searched temperature conversion. Convert body temperature, oven settings, weather forecasts, and more from Celsius to Fahrenheit with full formula steps.

°F = °C × 9/5 + 32
°F → °C

Fahrenheit to Celsius Converter

Convert US temperatures to the global standard. Perfect for understanding American weather, recipes, and fever readings in Celsius with clear step-by-step working.

°C = (°F − 32) × 5/9
°C → K

Celsius to Kelvin Converter

Essential for physics, chemistry, and engineering work. Convert everyday Celsius temperatures into the SI base unit Kelvin — used in all scientific calculations worldwide.

K = °C + 273.15
K → °C

Kelvin to Celsius Converter

Convert scientific Kelvin values into the familiar Celsius scale. Ideal for students and researchers interpreting lab data, thermodynamic results, or astronomy figures.

°C = K − 273.15
°F → K

Fahrenheit to Kelvin Converter

Convert American Fahrenheit readings directly into Kelvin for scientific use. Useful for US-based engineering and chemistry students working with SI units.

K = (°F + 459.67) × 5/9
K → °F

Kelvin to Fahrenheit Converter

Convert Kelvin values from scientific contexts back into Fahrenheit. Useful for US scientists, engineers, and students who need results in the Fahrenheit scale.

°F = K × 9/5 − 459.67

The 5 Temperature Scales Explained

Each scale was created for a different purpose — from everyday weather to quantum physics. Here is what you need to know about all five.

°C

Celsius

The most widely used scale worldwide. Defined by two fixed points: water freezes at 0 °C and boils at 100 °C at standard atmospheric pressure. Used in science, medicine, and everyday life in almost every country outside the US.

Freezing: 0 °C Boiling: 100 °C Body: 37 °C
°F

Fahrenheit

Primarily used in the United States. Water freezes at 32 °F and boils at 212 °F — a 180-degree span. Developed by Daniel Gabriel Fahrenheit in 1724 and still dominant in American weather, cooking, and medicine.

Freezing: 32 °F Boiling: 212 °F Body: 98.6 °F
K

Kelvin

The SI base unit of temperature used in physics, chemistry, and engineering. Starts at absolute zero — the theoretical minimum temperature. One kelvin equals exactly one degree Celsius in magnitude. No degree symbol is used with Kelvin.

Zero: 0 K = −273.15 °C Freezing: 273.15 K Boiling: 373.15 K
°R

Rankine

An absolute scale like Kelvin, but based on Fahrenheit-sized degrees. Zero Rankine is absolute zero. Used mainly in thermodynamics and aerospace engineering in the United States where Fahrenheit is the customary unit.

Zero: 0 °R = −459.67 °F Freezing: 491.67 °R Boiling: 671.67 °R
°Ré

Réaumur

A historical scale where water freezes at 0 °Ré and boils at 80 °Ré. Developed by René Antoine Ferchault de Réaumur in 1730 and once widely used across Europe. Largely obsolete today but still referenced in traditional cheese-making and historical scientific texts. One degree Réaumur equals 1.25 °C.

Freezing: 0 °Ré Boiling: 80 °Ré Body: 29.6 °Ré Absolute zero: −218.52 °Ré

Real-World Temperature Reference Guide

Understanding what temperatures feel like and mean in practice — from fever thresholds to oven settings to extreme science.

🌡️

Human Body & Health

  • Normal body temperature 37 °C / 98.6 °F
  • Mild fever 38 °C / 100.4 °F
  • High fever 39.5 °C / 103.1 °F
  • Hypothermia threshold 35 °C / 95 °F
  • Heatstroke risk 40+ °C / 104+ °F
🍳

Cooking & Baking

  • Water simmers 85–95 °C / 185–203 °F
  • Water boils (sea level) 100 °C / 212 °F
  • Medium oven 180 °C / 356 °F
  • Hot oven 220 °C / 428 °F
  • Deep fry oil 175 °C / 347 °F
🌍

Weather & Climate

  • Cold winter day −10 °C / 14 °F
  • Comfortable indoor 20–22 °C / 68–72 °F
  • Hot summer day 35 °C / 95 °F
  • Record high (Death Valley) 56.7 °C / 134.1 °F
  • Record low (Antarctica) −89.2 °C / −128.6 °F
🔬

Science & Engineering

  • Absolute zero −273.15 °C / 0 K
  • Liquid nitrogen −196 °C / −321 °F
  • Dry ice sublimation −78.5 °C / −109.3 °F
  • Steel melting range 1370–1510 °C
  • Surface of the Sun ~5,500 °C / ~9,932 °F

Why Use This Temperature Converter?

There are many converters online. Here is what sets this one apart.

⚡

Instant Results

Converts as you type — no button press needed. Results appear in under 120 ms on any device or network.

📐

Step-by-Step Working

Every conversion shows the exact formula and full calculation — ideal for students, teachers, and self-learners.

🌡️

All 5 Scales

Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur — including the two rare scales most converters skip entirely.

🚫

Validates Absolute Zero

Inputs below absolute zero are caught and flagged. You always get a physically valid result — not a nonsense number.

📱

Works on Any Device

Fully responsive — works seamlessly on phones, tablets, and desktops without installing an app.

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Free, No Account Needed

No sign-up, no ads, no cookies tracked. A clean, focused tool that just works every time.

Frequently Asked Questions

Quick, accurate answers to the most common temperature conversion questions.

The formula is °F = °C × 9/5 + 32. For example, 100 °C = 100 × 1.8 + 32 = 212 °F. A quick mental estimate: double the Celsius value and add 30 (e.g. 20 °C → 70 °F, actual 68 °F). For exact results use the converter above.
The formula is °C = (°F − 32) × 5/9. For example, 98.6 °F = (98.6 − 32) × 5/9 = 37 °C. This is the standard body temperature. To go back: °F = °C × 9/5 + 32.
The two scales meet at exactly −40°. At −40 °C, the temperature is also −40 °F. This is the only point where both scales give the identical reading. Try it in the converter above.
Add 273.15: K = °C + 273.15. For example, 25 °C = 25 + 273.15 = 298.15 K. To reverse: °C = K − 273.15. Kelvin starts at absolute zero, so no negative Kelvin values are possible.
The formula is K = (°F + 459.67) × 5/9. For example, 32 °F = (32 + 459.67) × 5/9 = 273.15 K. Kelvin to Fahrenheit: °F = K × 9/5 − 459.67.
Absolute zero is 0 K = −273.15 °C = −459.67 °F. It is the theoretical minimum temperature — the point at which particles have the minimum possible thermal energy. It is physically impossible to go below absolute zero. This converter flags any input below it as invalid.
Yes — 37 °C (98.6 °F) is the standard average human core body temperature. A normal range is 36.1 °C to 37.2 °C (97 °F – 99 °F) depending on the person, time of day, and measurement method. A temperature above 38 °C (100.4 °F) is generally considered a fever.
The US adopted Fahrenheit before the metric system became the global standard and never transitioned to Celsius in everyday use. Most countries switched in the 1960s–1970s as part of metrication. The US, Cayman Islands, and Liberia still use Fahrenheit for weather and daily life, though American scientific and medical research uses Celsius and Kelvin.
Both start at absolute zero, making them absolute scales. The difference is degree size: Kelvin uses Celsius-sized degrees, Rankine uses Fahrenheit-sized degrees. Formula: °R = K × 9/5. Rankine is used in US aerospace and thermodynamic engineering; Kelvin is the global scientific standard.
All results use exact conversion formulas computed to 10 decimal places of precision before display rounding. This exceeds the accuracy of any practical thermometer. The converter also validates all inputs against absolute zero, so every result is both mathematically and physically correct.

Ready to convert a temperature?

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