Convert Celsius, Fahrenheit, Kelvin, Rankine, Delisle, Newton, Reaumur, and Romer in seconds with formulas, examples, and clear reference points.
Formula
You can use this temperature conversion calculator in a few seconds, whether you are checking a weather report, converting an oven setting, or moving lab data from one scale to another.
Type the number you want to convert into the first field. You can enter whole numbers like 72 or decimals like 98.6, and the tool also handles negative values such as -18 for freezer temperatures.
Open the first menu and pick the scale you are starting with. Along with Celsius, Fahrenheit, and Kelvin, LiteCalc supports Rankine, Delisle, Newton, Reaumur, and Romer for specialized unit conversion work.
Select the unit you want to convert to in the second menu. The result updates right away, so you do not need to click a separate button. Use the swap icon when you want to reverse the calculation fast.
The formula box shows the math behind the answer. That helps you check a homework problem, confirm a cooking temperature, or learn how the conversion formula works instead of just copying the result.
Quick example
If you enter 180 and choose Celsius to Fahrenheit, the tool returns 356°F. That is a common oven setting in recipes written for different countries.
Why this matters
Temperature scales use different zero points and interval sizes. Without a reliable calculator, it is easy to misread a heat measurement and end up with a wrong thermostat setting, a failed recipe, or a lab note that does not match your source data.
A converted result is more useful when you know what it means in real life. These reference points help you judge whether the number describes freezing weather, safe food storage, or a science-only temperature scale.
Most everyday results fall into a few familiar bands. Around 20°C or 68°F feels like room temperature. Water freezes at 0°C or 32°F, and it boils at 100°C or 212°F at normal atmospheric pressure. In the Kelvin scale, those same points are 273.15 K and 373.15 K.
When you convert a number, check whether the answer fits the context. A body temperature of 37°C should come out as 98.6°F. A freezer temperature of -18°C should land at 0°F. Those familiar checkpoints make it easy to spot typing mistakes.
Kelvin deserves special attention because it is a thermodynamic scale, not a weather scale. You usually see Kelvin in science, engineering, and gas-law problems. It does not use a degree symbol, and its zero point is absolute zero, the coldest possible state in theory.
| Reference point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20 | 68 | 293.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Water boils | 100 | 212 | 373.15 |
If you want to know how to calculate temperature manually, the key idea is simple: some scales change the size of each step, and some also shift the zero point.
Celsius to Fahrenheit: (°C × 9/5) + 32
Fahrenheit to Celsius: (°F - 32) × 5/9
Celsius to Kelvin: °C + 273.15
Kelvin to Celsius: K - 273.15
Say you are following a recipe that lists an oven setting of 350°F, but your oven uses Celsius.
The same number in Kelvin is 176.67 + 273.15 = 449.82 K.
Celsius and Kelvin use the same step size, so moving between them is only a shift. You add or subtract 273.15 because the Kelvin scale begins at absolute zero. Fahrenheit is different because the interval size changes too. One Celsius degree equals 1.8 Fahrenheit degrees, which is why the formula uses 9/5 or 5/9.
For everyday estimates, many people use a shortcut. To turn Celsius into Fahrenheit quickly, double the Celsius value and add 30. It is not exact, but it gets you close enough for casual checks. For example, 20°C becomes about 70°F with the shortcut, while the exact answer is 68°F.
When precision matters, always use the exact formula or the calculator above. That is especially important for medical readings, baking temperatures, lab procedures, and engineering work where small errors can change the outcome.
Convert 25°C to Fahrenheit: (25 × 9/5) + 32 = 45 + 32 = 77°F. Convert it to Kelvin: 25 + 273.15 = 298.15 K. If your result is far away from those reference values, recheck the unit you selected.
Temperature conversion shows up in daily routines more often than you might think. These examples show how the same tool supports weather, health, cooking, travel, and science.
If a US weather app says 86°F, that converts to 30°C. This helps when you compare forecasts from different countries or plan travel with local weather data.
A recipe that calls for 180°C needs 356°F. Many cooks round that to 350°F or 355°F depending on the oven controls.
A reading of 101.3°F converts to 38.5°C. That is one reason health sites often include both scales, especially for fever guidance.
Recommended freezer storage is often listed as 0°F, which equals -18°C. That is a useful benchmark if your appliance uses metric controls.
Room temperature is often written as 298.15 K in chemistry because that equals 25°C. Kelvin is common when you work with gas laws, reaction rates, or thermodynamic scale equations.
In the United States, thermostats, oven dials, and weather forecasts usually use Fahrenheit. If you normally think in Celsius, keep a few anchor values in mind: 50°F is 10°C, 68°F is 20°C, and 77°F is 25°C.
One useful habit is to compare your answer to familiar reference points before you act on it. If an oven conversion lands near body temperature, or a freezer setting lands above room temperature, the wrong unit was probably selected. A quick logic check saves time and avoids mistakes.
One of the biggest content gaps on many calculator pages is context. This guide explains the scales and the benchmark values you are most likely to search for.
Celsius is the standard for weather and daily measurements in most countries. The freezing point of water is 0 and the boiling point is 100, which makes the scale easy to read for everyday use.
Fahrenheit is still common in the United States. Because the degrees are smaller, people often feel it gives more detail for everyday air temperature, thermostat settings, and cooking instructions.
Kelvin starts at absolute zero and uses the same interval size as Celsius. It is the preferred heat measurement unit in many science and engineering settings because it avoids negative values in thermodynamic equations.
LiteCalc supports several scales that many basic converters leave out. Rankine is an absolute scale like Kelvin but built on Fahrenheit-sized increments. Delisle, Newton, Reaumur, and Romer are older systems that still appear in historical notes, reference books, and some specialized academic problems.
That wider support matters when you are checking legacy engineering material or comparing multiple sources. Instead of hunting for a one-off formula every time, you can use one tool for all the common classroom and technical conversions.
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Common questions about temperature conversion, formulas, and scale differences.
Multiply the Celsius value by 9/5, then add 32. For example, 25°C becomes (25 × 9/5) + 32 = 77°F. This is the standard temperature conversion formula for moving from metric weather or cooking values to the US scale.
37°C equals 98.6°F. That is why 37°C is widely used as a normal body temperature reference point in health and first aid material.
The two scales meet at -40. If you convert -40°C to Fahrenheit, you get -40°F. It is one of the best-known reference points in temperature math.
Kelvin is an absolute thermodynamic scale, so the unit is shown as K rather than degrees K. Zero Kelvin marks absolute zero, which is why scientists prefer Kelvin in many formulas.
Absolute zero is -273.15°C, -459.67°F, and 0 K. It is the lowest theoretical temperature, where particle motion is at its minimum possible energy state.
Yes. Negative values are common in winter weather, freezer storage, and science problems. Enter the minus sign before the number and the calculator will apply the same exact formula.
Use Celsius for most global weather reports, metric recipes, and general science material. Use Fahrenheit for US weather forecasts, thermostats, and American cooking instructions. The calculator helps when you move between both systems.
Rankine is an absolute scale built on Fahrenheit-sized steps. It appears in some US engineering and thermodynamics work, where absolute temperature values are needed but calculations still align with Fahrenheit intervals.
A reliable online temperature calculator is exact to the displayed decimal places because the formulas are fixed. The only difference you may notice is rounding, such as showing 176.67°C instead of a longer decimal.