Temperature Converter

Temperature converter for Celsius, Fahrenheit, Kelvin, and Rankine

A temperature converter helps you translate a value from one temperature scale into another. That matters more often than people expect. Weather forecasts, ovens, thermostats, laboratory notes, manufacturing specifications, and engineering tables can all use different units. If you read 350°F on a recipe, 22°C on a room thermostat, or 300 K in a datasheet, you are looking at the same physical idea, but expressed using different reference points and step sizes. This calculator converts between Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R) and shows a practical breakdown so you can sanity-check the result.

To use the calculator, enter the temperature value, select the unit you are converting from, and select the unit you want to convert to. Press “Convert temperature.” You will get a primary result (the target unit) and a full set of equivalents across all supported scales. The full breakdown is useful because it quickly reveals obvious mistakes, such as converting 25°C and getting a negative Kelvin value, which cannot be correct because Kelvin is an absolute scale.

Behind the scenes, the conversion uses a simple, consistent approach. The input is first translated into Kelvin, then converted from Kelvin into your chosen output unit. Kelvin is used as the internal reference because it is an absolute temperature scale, meaning 0 K represents absolute zero, the theoretical minimum temperature. This approach avoids chaining multiple formulas and reduces the chance of logical errors when switching between units. The result is also easy to audit because every conversion passes through a single, consistent baseline.

Assumptions and how to use this calculator

• This tool converts temperature values only. It does not convert temperature differences (for example “a 10-degree increase”) where the offsets behave differently across some scales.
• Values below absolute zero are treated as invalid inputs because they do not represent a physically meaningful temperature. If your input falls below absolute zero for the selected unit, you will get an error.
• Results are shown to two decimal places for readability. If you need more precision (for example in lab work), treat the output as rounded and keep more significant figures in your own calculations.
• Celsius and Fahrenheit include an offset (their zero points are not absolute). Kelvin and Rankine are absolute scales where zero is absolute zero. This is why “adding” temperatures is usually not meaningful, while converting is.
• Rankine is included mainly for engineering contexts that use Fahrenheit-style increments but require an absolute scale. If you never use Rankine, you can ignore it and rely on Celsius, Fahrenheit, and Kelvin.

Common questions

Why does Celsius to Fahrenheit look “weird” compared to other conversions?

Because it is not a simple multiplication. Fahrenheit and Celsius have different step sizes and different zero points. Converting requires both a scale factor and an offset. That is why you see formulas like °F = (°C × 9/5) + 32. Conversions that involve Kelvin also include offsets when starting from or ending in Celsius or Fahrenheit.

What is the difference between Kelvin and Celsius?

They have the same step size, meaning a change of 1°C equals a change of 1 K. The difference is the zero point. Celsius is anchored to a human-friendly reference (water freezing point at 0°C under standard conditions), while Kelvin is anchored to absolute zero at 0 K. Because Kelvin is absolute, it is commonly used in science and engineering formulas.

Can I convert “temperature change” (like “increase by 10 degrees”) with this tool?

This tool converts absolute temperatures, not temperature differences. A temperature difference is how much a temperature changes, not where it is on the scale. For differences, offsets do not apply in the same way. For example, a 10°C increase equals an 18°F increase, but you would not add 32 in that case. If you are working with deltas, use the scale factor only.

Why does the calculator reject some negative numbers?

Negative temperatures are valid in Celsius and Fahrenheit. However, temperatures below absolute zero are not physically meaningful. Absolute zero is 0 K, which equals -273.15°C and -459.67°F (approximately). If you enter a value below that limit for the selected unit, the calculator blocks it to prevent impossible conversions.

How can I make my conversion more accurate?

Start with a more precise input value and avoid rounding too early. If you are copying from a device display, note whether it is already rounded (for example 72°F with no decimals). For scientific work, keep additional significant figures through your calculations and only round at the final reporting step. This calculator rounds the displayed result to two decimals to keep it readable for normal use.