Temperature Converter

The Temperature Converter converts between four temperature scales: Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R). Enter a value, select the source and target scales, and click Convert. The result is displayed immediately.

Temperature scales are used in very different contexts. Celsius and Fahrenheit are the two everyday scales — most of the world uses Celsius; the United States, its territories, and Belize primarily use Fahrenheit. Kelvin is the absolute temperature scale used in physics, chemistry, and engineering. Rankine is an absolute scale used in some US engineering applications. The converter handles all four and all direction combinations.

How to use the Temperature Converter

1. Enter the temperature value to convert.
2. Select the From scale — the scale your value is currently in (Celsius, Fahrenheit, Kelvin, or Rankine).
3. Select the To scale.
4. Click Convert. The result is displayed immediately.
5. To convert the same value to additional scales, change the To dropdown and click Convert again without re-entering the value.

The four temperature scales

Celsius (°C)

The international standard for everyday temperature measurement. Defined with 0°C as the freezing point of water and 100°C as the boiling point at standard atmospheric pressure (1 atm). Used in weather forecasts, cooking, and science in all countries except the United States, its territories, and Belize. Also called centigrade (a term that is technically still valid but is now rarely used in formal contexts).

Fahrenheit (°F)

The primary everyday temperature scale in the United States. Water freezes at 32°F and boils at 212°F. The 180-degree span between freezing and boiling (vs 100 degrees in Celsius) means Fahrenheit degrees are smaller than Celsius degrees: 1°C = 1.8°F. Human body temperature is approximately 98.6°F (37°C). Weather forecasts, oven temperatures in US recipes, and consumer appliance specifications in the US use Fahrenheit.

Kelvin (K)

The SI base unit of thermodynamic temperature. Kelvin uses the same degree size as Celsius but starts at absolute zero — the theoretical minimum temperature at which particles have minimum thermal energy. 0 K = -273.15°C = -459.67°F. No degree symbol is used with Kelvin; the unit is written as 'K' not '°K'. Kelvin is used in all scientific and engineering calculations where absolute temperature is required — thermodynamics, gas laws (PV = nRT), blackbody radiation, and cryogenics.

Rankine (°R)

An absolute temperature scale that uses Fahrenheit-sized degrees rather than Celsius-sized degrees. 0°R = absolute zero = 0 K = -273.15°C. Water freezes at 491.67°R and boils at 671.67°R. Rankine is used primarily in US engineering, particularly in aerospace, thermodynamics textbooks, and some industrial applications where absolute temperature is needed but Fahrenheit units are preferred. Outside the US, Kelvin is used instead.

Kelvin and Rankine are both absolute scales — they both start at absolute zero (0 K = 0°R). Celsius and Fahrenheit are relative scales — their zero points are defined by water behavior, not physical minimums. Because Kelvin and Celsius use the same degree size, converting between them is a simple addition/subtraction of 273.15. Because Fahrenheit and Rankine use the same degree size, converting between them is a simple addition/subtraction of 459.67.

Conversion formulas for all six direction pairs

The table below shows all conversion formulas with worked examples. These are the exact formulas the converter uses:

Reference temperature table

The table below shows common reference temperatures across all four scales. Use it to quickly verify a conversion result or to get an intuitive sense of what a temperature means in each scale:

Oven temperature quick reference — cooking conversions

The most common everyday use of the temperature converter is translating oven temperatures between Celsius and Fahrenheit when following international recipes. The table below covers the standard oven temperature range with descriptions and typical uses. Fan-assisted ovens run hotter by approximately 20°C — the fan temperature is shown in parentheses:

Usage limits

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Frequently asked questions

What is the formula to convert Celsius to Fahrenheit?

F = (C x 9/5) + 32 — or equivalently F = (C x 1.8) + 32. To convert in the other direction (Fahrenheit to Celsius): C = (F - 32) x 5/9 — or equivalently C = (F - 32) / 1.8. Example: 25°C to Fahrenheit = (25 x 1.8) + 32 = 45 + 32 = 77°F. Example: 77°F to Celsius = (77 - 32) / 1.8 = 45 / 1.8 = 25°C.

What is the difference between Celsius and Fahrenheit?

Celsius and Fahrenheit are both relative temperature scales used for everyday measurements, but they have different reference points and different degree sizes. Celsius: 0°C = freezing point of water, 100°C = boiling point. Fahrenheit: 32°F = freezing point, 212°F = boiling point. One Celsius degree is 1.8 times larger than one Fahrenheit degree. Celsius is used worldwide except in the United States, where Fahrenheit remains standard for weather, cooking, and consumer contexts.

Why does Kelvin not use a degree symbol?

Kelvin is the SI base unit of thermodynamic temperature — it is an absolute scale starting at the theoretical minimum temperature (absolute zero = 0 K). By SI convention, the unit is written as 'K' without a degree symbol, unlike Celsius (°C) and Fahrenheit (°F). The reasoning is that Kelvin is a true physical unit measurement (like meters or kilograms) rather than a position on a scale relative to an arbitrary reference point. Saying '300 K' is like saying '300 meters’ — the unit stands alone.

What is absolute zero?

Absolute zero is the theoretical minimum temperature — the point at which a system has minimum thermal energy and its particles have minimum kinetic energy. It is defined as 0 K = -273.15°C = -459.67°F = 0°R. Absolute zero has never been reached in practice; the lowest recorded laboratory temperatures are within fractions of a nanokelvin above it. At absolute zero, quantum mechanical effects prevent total cessation of particle motion (zero-point energy), so there is a quantum mechanical minimum even at 0 K.

What is Rankine and when is it used?

Rankine is an absolute temperature scale that uses Fahrenheit-sized degrees. Like Kelvin, it starts at absolute zero (0°R = 0 K), but each degree is the same size as a Fahrenheit degree rather than a Celsius degree. Water freezes at 491.67°R and boils at 671.67°R. Rankine is used in US aerospace engineering, some thermodynamics textbooks, and industrial applications where absolute temperature is needed but the engineer is working in Fahrenheit units. Outside the United States, Kelvin is universally preferred for scientific absolute temperature calculations.

What oven temperature is 350°F in Celsius?

350°F = (350 - 32) / 1.8 = 318 / 1.8 = 176.7°C, conventionally rounded to 175-180°C. This is a moderate oven temperature, commonly used for cakes, cookies, and standard baking. For fan-assisted (convection) ovens, reduce by approximately 20°C: 350°F corresponds to approximately 155-160°C on fan setting. The oven temperature quick reference table above covers the full range of cooking temperatures in both scales.

At what temperature are Celsius and Fahrenheit the same?

Celsius and Fahrenheit are equal at -40 degrees: -40°C = -40°F. This is the only point where both scales give the same numerical reading. You can verify this with the formula: F = (C x 1.8) + 32 = (-40 x 1.8) + 32 = -72 + 32 = -40. At temperatures above -40, Fahrenheit numbers are always higher than the corresponding Celsius number; below -40, Fahrenheit numbers are lower (more negative) than Celsius.

Is the Temperature Converter free?

Yes. The converter is free within the daily usage limits shown above. Guest users can perform 25 conversions per day without creating an account. Registering a free ToolsPiNG account increases the daily limit to 100 conversions per day.