Temperature Converter — Celsius, Fahrenheit & Kelvin

A temperature converter translates between the three primary temperature scales — Celsius (°C), Fahrenheit (°F), and Kelvin (K) — using exact mathematical formulas. Celsius and Fahrenheit are the everyday scales used in weather forecasting, cooking, and human body temperature measurement. Kelvin is the absolute thermodynamic scale used in physics, chemistry, astronomy, and engineering. All three scales measure the same physical quantity — thermal energy — from different zero points and with different degree sizes.

Temperature is the most commonly measured physical quantity in daily life. Weather apps report in Celsius or Fahrenheit depending on country. Ovens in the U.S. display Fahrenheit while European ovens display Celsius. Medical thermometers may read in either system. International travelers routinely need to convert: a forecast of 30°C sounds mild only if you know it is 86°F. A body temperature of 102°F sounds alarming — but 38.9°C puts it in clinical context more precisely. Recipes from different countries require temperature conversion before cooking.

Beyond everyday use, temperature conversion is critical in science and engineering. The ideal gas law, blackbody radiation equations, thermodynamic efficiency calculations, and chemical equilibrium constants all require temperature in Kelvin. A laboratory researcher working with Celsius measurements must convert to Kelvin before using these equations. This converter handles all three scales with exact formulas, enabling both practical daily conversions and scientific applications.

Example 1 — Weather conversion: 20°C (comfortable spring day) = (20 × 1.8) + 32 = 36 + 32 = 68°F -10°C (cold winter day) = (-10 × 1.8) + 32 = -18 + 32 = 14°F 35°C (hot summer day) = (35 × 1.8) + 32 = 63 + 32 = 95°F

Example 2 — Cooking temperatures: 180°C (standard baking) = (180 × 1.8) + 32 = 324 + 32 = 356°F ≈ 350°F (rounded in recipes) 200°C (high heat roasting) = 392°F 220°C (pizza oven) = 428°F

Example 3 — Medical temperatures: 36.6°C (normal body temp) = (36.6 × 1.8) + 32 = 65.88 + 32 = 97.88°F ≈ 97.9°F 38.5°C (moderate fever) = (38.5 × 1.8) + 32 = 69.3 + 32 = 101.3°F 40°C (high fever) = 104°F — requires medical attention

Example 4 — Kelvin conversions for science: 25°C (standard lab temperature) = 25 + 273.15 = 298.15 K Liquid nitrogen: −196°C = 77.15 K Surface of Sun: 5,778 K = 5,778 − 273.15 = 5,504.85°C = 9,940.73°F

Temperature scales shape how entire populations perceive climate, health, and cooking. For anyone who travels internationally, works with international colleagues, reads foreign recipes, or consumes news from countries using a different scale, temperature conversion is a daily practical need. The gap between Fahrenheit intuition and Celsius reality causes real confusion: a tourist from the U.S. in Europe sees a weather forecast of 28°C and has no immediate sense of whether to wear a jacket. A European in the U.S. sees 72°F and must consciously convert to understand it is a pleasant 22°C day.

In healthcare, temperature precision and scale matters for patient safety. The clinical definition of fever (≥38°C or ≥100.4°F) requires accurate conversion when records from different healthcare systems are involved. Drug storage requirements are specified in both Celsius and Fahrenheit on pharmaceutical labels in the U.S.; a vaccine stored in a refrigerator calibrated in Fahrenheit and required to be kept at 2–8°C must be correctly converted to 35.6–46.4°F to ensure proper storage. Temperature monitoring failures due to unit confusion have caused vaccine spoilage and drug degradation in clinical settings.

In science and engineering, using the wrong temperature scale in thermodynamic equations produces completely wrong results. The ideal gas law (PV = nRT) requires absolute temperature — any calculation using Celsius instead of Kelvin introduces a systematic error proportional to the 273.15 K offset. For near-absolute-zero experiments, this error is enormous (a measurement of 1°C used as '1 K' instead of '274 K' is off by a factor of 274). For combustion temperatures (1,000°C+), the proportional error is smaller but still significant in precision engineering. The Kelvin scale is not an abstraction — it is the required unit for thermodynamic work.

This converter handles the three main temperature scales: Celsius, Fahrenheit, and Kelvin. It does not include the Rankine scale (°R = °F + 459.67), which is the Fahrenheit-based absolute temperature scale used in some U.S. engineering applications (thermodynamic calculations in non-metric engineering software, HVAC system design). For U.S. engineering contexts requiring Rankine, the conversion is: °R = K × 1.8.

The converter does not include the Réaumur scale (°Ré = °C × 4/5), a historical scale still occasionally encountered in old European scientific literature, winemaking, and some cheesemaking traditions. The Rømer and Delisle scales, invented before Celsius and Fahrenheit were standardized, appear in historical scientific texts but have no modern practical use.

This converter also does not model the effects of pressure on temperature for phase transitions. Water boils at 100°C only at sea level (1 atm). At higher altitudes or in pressurized environments, the boiling point changes significantly (see FAQ above). Similarly, the melting point of water depends slightly on pressure. For pressure-sensitive applications — autoclave sterilization, pressure cooking, altitude cooking — the boiling/freezing points shown as reference values should be adjusted for actual conditions.