Temperature Converter

°C (Celsius) · °F (Fahrenheit) · K (Kelvin) · °R (Rankine) · °Ré (Réaumur)

Convert temperature units instantly — Celsius, Fahrenheit, Kelvin, Rankine and Réaumur. Essential for everyday cooking, scientific research, weather, medicine and engineering work across metric and imperial systems.

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100°C =

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°F = °C × 9/5 + 32 | °C = (°F − 32) × 5/9 | K = °C + 273.15 | −40°C = −40°F

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Reference Table — from selected unit

Symbol	Scale	Value

Formula:

About Temperature Scales

Temperature is one of the fundamental physical quantities, measuring the thermal energy state of matter. Five distinct scales exist: Celsius and Fahrenheit for everyday use, Kelvin and Rankine as absolute (zero-based) scientific scales, and Réaumur as a historical relic still found in certain cheese-making and winemaking traditions. Because temperature conversions are non-linear offset functions — not simple multiplications — an online converter is far more reliable than rough mental estimates for anything beyond common reference points.

🌍 Everyday Scales — °C and °F

The Celsius scale (°C) was developed by Swedish astronomer Anders Celsius in 1742, defining water's freezing point as 0° and boiling point as 100° at sea level. It is the standard temperature scale in 195 of 197 countries worldwide and used in all scientific and medical contexts. Fahrenheit (°F) was proposed by Daniel Gabriel Fahrenheit in 1724, originally using brine freezing (0°F), human body temperature (96°F), and the boiling point of water (212°F). It remains the primary scale in the United States, Cayman Islands and a few other territories, and is commonly used in weather, cooking and everyday conversation in those regions.

🔬 Scientific Scales — K, °R and °Ré

The Kelvin scale (K), proposed by Lord Kelvin in 1848, is the SI base unit of temperature. Starting at absolute zero (0 K = −273.15°C), it uses Celsius-sized degree increments. All thermodynamic equations require Kelvin — gas laws, heat transfer, black-body radiation. The Rankine scale (°R) is the imperial equivalent: absolute zero starting point with Fahrenheit-sized increments (0°R = 0 K; 1°R = 1°F difference). Rankine is used in some US engineering fields. The Réaumur scale (°Ré), devised by René Antoine Ferchault de Réaumur in 1730, defines water's freezing point as 0°Ré and boiling as 80°Ré. While obsolete in science, it persists in cheese-making texts across France, Italy and parts of Eastern Europe.

Why temperature conversion is different from other unit conversions: Most unit conversions are a simple multiplication (multiply metres by 3.281 to get feet). Temperature scales have different zero points, so you must apply a two-step offset formula. For example, 0°C ≠ 0°F — you must subtract 32 then multiply by 5/9. This is why approximate mental shortcuts ("double it and add 30" for °C→°F) are only accurate near room temperature.

Quick Temperature Conversions

0°C → °F

0°C = 32°F (water freezing point)

100°C → °F

100°C = 212°F (water boiling point)

37°C → °F

37°C = 98.6°F (normal body temperature)

98.6°F → °C

98.6°F = 37°C (body temperature)

0°C → K

0°C = 273.15 K (water freezing)

0 K → °C

0 K = −273.15°C (absolute zero)

−40°F → °C

−40°F = −40°C (only equal point)

20°C → °F

20°C = 68°F (room temperature)

180°C → °F

180°C = 356°F (oven baking)

Worked Examples

Cooking / Baking

180°C → °F
°F = (180 × 9/5) + 32 = 356°F

A recipe calls for 180°C — the standard baking temperature for cakes and bread. US ovens display Fahrenheit, so 356°F is the equivalent. Most US bakers round to 350°F (177°C) as a practical approximation.

Weather / Travel

35°C → °F
°F = (35 × 9/5) + 32 = 95°F

A weather forecast in India says 35°C for summer. An American traveller converts this to 95°F — recognising it as an extremely hot day requiring hydration, sun protection and limiting outdoor activity.

Scientific / Cryogenics

−196°C → K
K = −196 + 273.15 = 77.15 K

Liquid nitrogen boils at −196°C = 77.15 K. Physicists always work in Kelvin for thermodynamic calculations. This temperature is used for cryopreservation, semiconductor cooling and superconductor research.

Engineering / Rankine

500°F → °R
°R = 500 + 459.67 = 959.67°R

A US combustion engineer works with exhaust gas at 500°F. In thermodynamic cycle calculations using US units, they need 959.67°R for Rankine-based equations — the imperial equivalent of using Kelvin in SI systems.

Explore All Temperature Conversions

°C → °F °F → °C °C → K K → °C °F → K K → °F °C → °R °R → °C °F → °R °R → °F K → °R °R → K °C → °Ré °Ré → °C °F → °Ré °Ré → °F K → °Ré °Ré → K

Who Uses a Temperature Converter?

🍳

Home Cooks & Bakers

Convert oven temperatures between Celsius (European recipes) and Fahrenheit (American recipes) — the most common everyday temperature conversion worldwide.

✈️

Travellers & Expats

Interpret local weather forecasts — Americans reading Celsius forecasts abroad, or non-Americans visiting the US and seeing unfamiliar Fahrenheit values on weather apps.

🏥

Healthcare Professionals

Convert body temperature readings between °C and °F for international patient records, medical device calibration, and pharmaceutical storage requirements.

🔬

Scientists & Researchers

Convert to Kelvin for thermodynamic equations, gas law calculations, spectroscopy and any experiment where an absolute temperature scale is required.

⚙️

Engineers

US engineers use Rankine in thermodynamic cycles; international engineers use Kelvin. Converting between °F, °R, °C and K is routine in heat transfer and fluid mechanics work.

🧀

Food Industry & Artisans

Traditional European cheesemakers and winemakers may encounter Réaumur temperatures in legacy recipes and regional standards — converting to °C for modern process control.

Mental Math Tips — Temperature

°C → °F

Double and add 30 for a quick estimate (accurate within 5°F between 0–30°C). For precision: multiply by 1.8 and add 32. Memorise anchor points: 0°C=32°F, 20°C=68°F, 37°C=98.6°F, 100°C=212°F.

°F → °C

Subtract 30 and halve for a rough estimate. For precision: subtract 32 then multiply by 0.556 (or 5/9). Key reference: 98.6°F=37°C, 32°F=0°C, 212°F=100°C. Remember −40 is the crossover point.

°C → K

Simply add 273 (precise: 273.15). Room temperature 20°C = 293 K. Absolute zero 0 K = −273°C. This is the only temperature conversion that doesn't require multiplication — just a constant offset.

Frequently Asked Questions — Temperature Converter

Use the formula: °F = (°C × 9/5) + 32. For example, 100°C = (100 × 9/5) + 32 = 212°F (boiling point of water at sea level). For body temperature: 37°C = (37 × 9/5) + 32 = 98.6°F.

Use the formula: °C = (°F − 32) × 5/9. For example, 98.6°F = (98.6 − 32) × 5/9 = 37°C (normal body temperature). Freezing point: 32°F = (32 − 32) × 5/9 = 0°C.

Add 273.15 to the Celsius value: K = °C + 273.15. For example, 0°C = 273.15 K (water freezing point) and 100°C = 373.15 K (water boiling point). Kelvin is always positive — there is no negative Kelvin.

Absolute zero is 0 Kelvin = −273.15°C = −459.67°F. It is the lowest theoretically possible temperature, at which all atomic motion ceases. It has never been achieved in practice, though scientists have reached within a billionth of a degree of it.

Celsius and Fahrenheit are equal at −40°. That is, −40°C = −40°F. This is the only point where both scales intersect, which is a useful mnemonic for extreme cold weather comparisons.

Both Kelvin and Rankine are absolute temperature scales starting at absolute zero. Kelvin uses Celsius-sized degrees (1 K = 1°C increment) while Rankine uses Fahrenheit-sized degrees (1°R = 1°F increment). Convert with: °R = K × 9/5. Water freezes at 273.15 K = 491.67°R.

The Réaumur scale (°Ré) was widely used in 18th-century Europe. Water freezes at 0°Ré and boils at 80°Ré. Convert to Celsius: °C = °Ré × 5/4. Convert from Celsius: °Ré = °C × 4/5. So 20°C = 16°Ré. Réaumur is now obsolete but still appears in historical texts and some traditional cheesemaking.

Temperature Reference Points

Common temperature reference points across Celsius, Fahrenheit and Kelvin scales.

Temperature	Celsius	Fahrenheit	Kelvin
Absolute zero	−273.15°C	−459.67°F	0 K
Liquid nitrogen	−196°C	−320.8°F	77.15 K
Dry ice (CO₂)	−78.5°C	−109.3°F	194.65 K
Water freezing	0°C	32°F	273.15 K
Room temperature	20°C	68°F	293.15 K
Body temperature	37°C	98.6°F	310.15 K
Water boiling	100°C	212°F	373.15 K
Oven (baking)	180°C	356°F	453.15 K
Sun surface	5,505°C	9,941°F	5,778 K