Temperature is one of the most common measurements used in everyday life, science, engineering, weather forecasting, cooking, medicine, manufacturing, and countless other applications. However, temperature can be expressed using different scales, and converting between them manually can sometimes be confusing.
Degree Conversion Calculator
The three temperature scales most commonly encountered are Celsius (°C), Fahrenheit (°F), and Kelvin (K). Celsius is widely used around the world for everyday temperatures, Fahrenheit remains common in the United States, and Kelvin is heavily used in scientific and technical applications.
Our Degree Conversion Calculator makes it easy to convert a temperature from one scale to another. You can enter a temperature, select the original unit, select the unit you want to convert to, and instantly get the converted result.
Whether you need to convert Celsius to Fahrenheit, Fahrenheit to Celsius, Celsius to Kelvin, Kelvin to Celsius, Fahrenheit to Kelvin, or Kelvin to Fahrenheit, understanding the underlying formulas can help you make accurate calculations and interpret temperature values correctly.
This guide explains how the calculator works, the formulas behind temperature conversion, practical examples, common temperature references, useful conversion tables, and important differences between temperature scales.
What Is Temperature Conversion?
Temperature conversion is the process of expressing the same temperature using a different temperature scale.
For example, water freezes at:
- 0°C
- 32°F
- 273.15 K
These three values look completely different, but they represent the same physical temperature.
Temperature scales have different zero points and different numerical intervals. Because of this, conversion is not always a simple multiplication or division.
For Celsius and Fahrenheit, both the starting point and the size of a degree differ. Kelvin uses the same degree-size interval as Celsius but begins from absolute zero.
A degree conversion calculator accounts for these differences automatically.
Understanding the Three Main Temperature Scales
Celsius (°C)
The Celsius scale is one of the most widely used temperature scales in the world.
It is commonly used for:
- Weather forecasts
- Household thermostats
- Cooking
- Refrigeration
- Medical temperature readings
- Industrial measurements
- Everyday temperature descriptions
On the Celsius scale, water freezes at 0°C and boils at approximately 100°C at standard atmospheric pressure.
The Celsius scale is especially convenient for everyday temperature measurements because the freezing and boiling points of water provide familiar reference points.
Fahrenheit (°F)
The Fahrenheit scale is primarily used for everyday temperature measurements in the United States and a few other locations.
Common examples include:
- Weather temperatures
- Body temperature
- Oven settings
- Air-conditioning settings
- Household thermometers
Water freezes at 32°F and boils at approximately 212°F at standard atmospheric pressure.
This means that the interval between the freezing and boiling points of water is 180 Fahrenheit degrees compared with 100 Celsius degrees.
Kelvin (K)
The Kelvin scale is commonly used in science, physics, chemistry, engineering, and other technical fields.
Unlike Celsius and Fahrenheit, Kelvin is an absolute temperature scale. Its zero point corresponds to absolute zero, the theoretical lower limit of thermodynamic temperature.
Kelvin does not normally use a degree symbol. For example:
300 K
rather than:
300°K
One Kelvin has the same size increment as one degree Celsius. The difference is the position of zero.
The relationship is:
0°C = 273.15 K
Therefore:
K = °C + 273.15
How to Use the Degree Conversion Calculator
The calculator is designed to make temperature conversion quick and straightforward.
Step 1: Enter the Temperature
Enter the temperature value you want to convert into the Enter Temperature field.
You can enter whole numbers or decimal values, such as:
- 25
- 98.6
- -10
- 37.5
- 300.15
The calculator accepts negative Celsius and Fahrenheit temperatures. Kelvin values, however, cannot be below absolute zero.
Step 2: Select the Original Unit
Under Convert From, select the temperature scale of the value you entered.
You can choose:
- Celsius (°C)
- Fahrenheit (°F)
- Kelvin (K)
For example, if you enter 25 and the original value is 25°C, select Celsius.
Step 3: Select the Target Unit
Under Convert To, select the temperature scale you want.
For example:
Convert From: Celsius
Convert To: Fahrenheit
Step 4: Click Calculate
Click the Calculate button.
The calculator will display the converted temperature and provide a conversion statement showing both the original value and the result.
For example:
25.00 °C = 77.00 °F
Step 5: Start a New Conversion
Use the Reset button when you want to clear the previous calculation and perform a different conversion.
Celsius to Fahrenheit Formula
One of the most commonly requested temperature conversions is Celsius to Fahrenheit.
The formula is:
°F = (°C × 9/5) + 32
You first multiply the Celsius temperature by 9/5 and then add 32.
Example
Convert 25°C to Fahrenheit.
°F = (25 × 9/5) + 32
°F = 45 + 32
°F = 77°F
Therefore:
25°C = 77°F
Fahrenheit to Celsius Formula
To convert Fahrenheit to Celsius, use:
°C = (°F − 32) × 5/9
First subtract 32 from the Fahrenheit temperature and then multiply by 5/9.
Example
Convert 68°F to Celsius.
°C = (68 − 32) × 5/9
°C = 36 × 5/9
°C = 20°C
Therefore:
68°F = 20°C
Celsius to Kelvin Formula
The Celsius-to-Kelvin conversion is particularly simple because both scales have the same degree interval.
The formula is:
K = °C + 273.15
Example
Convert 25°C to Kelvin.
K = 25 + 273.15
K = 298.15 K
Therefore:
25°C = 298.15 K
Kelvin to Celsius Formula
To convert Kelvin to Celsius:
°C = K − 273.15
Example
Convert 300 K to Celsius.
°C = 300 − 273.15
°C = 26.85°C
Therefore:
300 K = 26.85°C
Fahrenheit to Kelvin Formula
You can convert Fahrenheit to Kelvin in two stages or use the combined formula.
The formula is:
K = (°F − 32) × 5/9 + 273.15
Example
Convert 32°F to Kelvin.
K = (32 − 32) × 5/9 + 273.15
K = 273.15 K
Therefore:
32°F = 273.15 K
Kelvin to Fahrenheit Formula
To convert Kelvin to Fahrenheit:
°F = (K − 273.15) × 9/5 + 32
Example
Convert 300 K to Fahrenheit.
°F = (300 − 273.15) × 9/5 + 32
°F = 26.85 × 1.8 + 32
°F = 80.33°F
Therefore:
300 K ≈ 80.33°F
Degree Conversion Formula Summary
The following table summarizes the formulas used for converting among Celsius, Fahrenheit, and Kelvin.
| Conversion | Formula |
|---|---|
| Celsius to Fahrenheit | °F = (°C × 9/5) + 32 |
| Fahrenheit to Celsius | °C = (°F − 32) × 5/9 |
| Celsius to Kelvin | K = °C + 273.15 |
| Kelvin to Celsius | °C = K − 273.15 |
| Fahrenheit to Kelvin | K = (°F − 32) × 5/9 + 273.15 |
| Kelvin to Fahrenheit | °F = (K − 273.15) × 9/5 + 32 |
Knowing these six formulas allows you to convert virtually any temperature among the three scales.
Common Temperature Conversion Table
A reference table can be useful when you need a quick estimate without performing a calculation.
| Celsius | Fahrenheit | Kelvin |
|---|---|---|
| -40°C | -40°F | 233.15 K |
| -20°C | -4°F | 253.15 K |
| -10°C | 14°F | 263.15 K |
| 0°C | 32°F | 273.15 K |
| 5°C | 41°F | 278.15 K |
| 10°C | 50°F | 283.15 K |
| 15°C | 59°F | 288.15 K |
| 20°C | 68°F | 293.15 K |
| 25°C | 77°F | 298.15 K |
| 30°C | 86°F | 303.15 K |
| 35°C | 95°F | 308.15 K |
| 37°C | 98.6°F | 310.15 K |
| 40°C | 104°F | 313.15 K |
| 50°C | 122°F | 323.15 K |
| 75°C | 167°F | 348.15 K |
| 100°C | 212°F | 373.15 K |
This table can help with quick comparisons, but the calculator is more convenient for unusual or decimal temperature values.
Important Temperature Reference Points
Understanding familiar temperatures makes it easier to interpret converted results.
Absolute Zero
Absolute zero is:
0 K = -273.15°C = -459.67°F
This represents the theoretical lower limit of thermodynamic temperature.
A Kelvin temperature cannot be negative. This is why the calculator prevents values below 0 K.
Water Freezing Point
At standard atmospheric pressure:
0°C = 32°F = 273.15 K
This is one of the most useful reference points for understanding the differences among the scales.
Comfortable Indoor Temperature
A typical indoor temperature might be around:
20–25°C
This corresponds approximately to:
68–77°F
and:
293.15–298.15 K
The exact preferred indoor temperature varies by individual, season, building, clothing, and activity.
Human Body Temperature
A commonly cited nominal body temperature is:
37°C = 98.6°F = 310.15 K
Actual body temperature can naturally vary depending on the individual, measurement method, time of day, and other factors.
Water Boiling Point
At standard atmospheric pressure:
100°C = 212°F = 373.15 K
The boiling point changes with atmospheric pressure, so 100°C should not be treated as the boiling point under every possible condition.
Worked Example: Convert -10°C to Fahrenheit
Suppose a weather report gives a temperature of -10°C, but you want to understand it in Fahrenheit.
Use:
°F = (°C × 9/5) + 32
Substitute -10:
°F = (-10 × 9/5) + 32
°F = -18 + 32
°F = 14°F
Therefore:
-10°C = 14°F
This conversion is particularly useful when comparing international weather reports.
Worked Example: Convert 98.6°F to Celsius
Suppose a temperature is given as 98.6°F.
Use:
°C = (°F − 32) × 5/9
Substitute:
°C = (98.6 − 32) × 5/9
°C = 66.6 × 5/9
°C = 37°C
Therefore:
98.6°F = 37°C
Worked Example: Convert 25°C to Kelvin
For Celsius to Kelvin:
K = °C + 273.15
Therefore:
K = 25 + 273.15
K = 298.15 K
So:
25°C = 298.15 K
This type of conversion is frequently encountered in scientific calculations.
Why Fahrenheit and Celsius Use Different Numbers
The Celsius and Fahrenheit scales have different reference points and different degree sizes.
For Celsius, water freezes at 0°C and boils at 100°C under standard atmospheric pressure.
For Fahrenheit, water freezes at 32°F and boils at 212°F under the same general reference condition.
The range between freezing and boiling is therefore:
- 100 Celsius degrees
- 180 Fahrenheit degrees
Consequently:
1°C = 1.8°F as a temperature interval.
However, this does not mean you can convert an actual Celsius temperature simply by multiplying by 1.8. The different zero points mean that the +32 adjustment is also required.
Temperature Difference vs. Temperature Conversion
An important distinction is the difference between converting a temperature and converting a temperature interval.
For absolute temperatures:
25°C = 77°F
But when discussing temperature changes, the relationship is different.
For example, a change of:
10°C
corresponds to a change of:
18°F
because:
10 × 9/5 = 18
There is no +32 in a temperature-difference conversion.
This distinction is important in science, weather analysis, engineering, and calculations involving changes in temperature.
Why Kelvin Is Important in Science
Kelvin is particularly valuable because it provides an absolute temperature scale.
Many scientific equations require absolute temperature rather than Celsius or Fahrenheit.
For example, calculations involving thermodynamics, gas behavior, radiation, and statistical mechanics often use Kelvin.
A Celsius temperature can be negative, but a thermodynamic temperature expressed in Kelvin cannot be below zero.
The relationship between Celsius and Kelvin is straightforward:
K = °C + 273.15
For example:
27°C = 300.15 K
Using Kelvin helps avoid problems caused by arbitrary zero points.
Practical Uses of a Degree Conversion Calculator
A temperature conversion calculator can be useful in many situations.
Weather
International weather reports may use Celsius while U.S. weather information often uses Fahrenheit. Converting between the scales makes it easier to understand unfamiliar forecasts.
Cooking
Recipes, ovens, and cooking equipment can use different temperature scales. Converting oven temperatures is especially useful when following recipes from another country.
Science and Education
Students frequently encounter temperature conversions in physics, chemistry, biology, and mathematics.
Engineering
Engineers may need to convert temperatures when working with international specifications, technical documentation, material properties, or thermal systems.
HVAC
Heating, ventilation, and air-conditioning systems may use different units depending on the manufacturer and market.
Manufacturing
Industrial processes often require precise temperature control, making accurate conversions important when equipment and specifications use different measurement systems.
Travel
Travelers moving between countries may encounter unfamiliar temperature scales in weather forecasts, accommodation information, or local services.
Tips for Accurate Temperature Conversion
Although the formulas are straightforward, several common mistakes are worth avoiding.
Remember the 32 Offset
When converting Celsius to Fahrenheit, you must add 32 after multiplying by 9/5.
For Fahrenheit to Celsius, subtract 32 before multiplying by 5/9.
Leaving out the 32 adjustment produces an incorrect result.
Do Not Use a Degree Symbol With Kelvin
The standard notation is:
300 K
rather than:
300°K
Celsius and Fahrenheit use degree symbols, while Kelvin is written simply as K.
Be Careful With Negative Temperatures
Negative Celsius and Fahrenheit values are valid.
For example:
-40°C = -40°F
This is a unique point where the Celsius and Fahrenheit scales have the same numerical value.
Kelvin, however, cannot be negative.
Consider the Appropriate Precision
The calculator provides the converted result to two decimal places. This is usually convenient for everyday use.
For technical calculations, it may be appropriate to retain additional precision before rounding the final result.
Common Celsius to Fahrenheit Conversions
Here are several frequently used values:
| Celsius | Fahrenheit |
|---|---|
| -40°C | -40°F |
| -30°C | -22°F |
| -20°C | -4°F |
| -10°C | 14°F |
| 0°C | 32°F |
| 10°C | 50°F |
| 20°C | 68°F |
| 25°C | 77°F |
| 30°C | 86°F |
| 37°C | 98.6°F |
| 40°C | 104°F |
| 50°C | 122°F |
These values can serve as a quick reference for everyday temperature comparisons.
Common Fahrenheit to Celsius Conversions
| Fahrenheit | Celsius |
|---|---|
| -40°F | -40°C |
| 0°F | -17.78°C |
| 14°F | -10°C |
| 32°F | 0°C |
| 50°F | 10°C |
| 59°F | 15°C |
| 68°F | 20°C |
| 77°F | 25°C |
| 86°F | 30°C |
| 98.6°F | 37°C |
| 104°F | 40°C |
| 122°F | 50°C |
| 212°F | 100°C |
Common Celsius to Kelvin Conversions
Because Celsius and Kelvin have the same size increments, each conversion simply adds 273.15.
| Celsius | Kelvin |
|---|---|
| -40°C | 233.15 K |
| -20°C | 253.15 K |
| 0°C | 273.15 K |
| 10°C | 283.15 K |
| 20°C | 293.15 K |
| 25°C | 298.15 K |
| 30°C | 303.15 K |
| 37°C | 310.15 K |
| 50°C | 323.15 K |
| 100°C | 373.15 K |
Frequently Asked Questions
1. What is a Degree Conversion Calculator?
A Degree Conversion Calculator is a tool that converts a temperature from one scale to another. This calculator supports Celsius, Fahrenheit, and Kelvin conversions.
2. How do I convert Celsius to Fahrenheit?
Use the formula:
°F = (°C × 9/5) + 32
For example, 20°C equals 68°F.
3. How do I convert Fahrenheit to Celsius?
Use:
°C = (°F − 32) × 5/9
For example, 68°F equals 20°C.
4. How do I convert Celsius to Kelvin?
Add 273.15 to the Celsius temperature:
K = °C + 273.15
For example, 25°C equals 298.15 K.
5. How do I convert Kelvin to Celsius?
Subtract 273.15:
°C = K − 273.15
For example, 300 K equals 26.85°C.
6. How do I convert Fahrenheit to Kelvin?
Use:
K = (°F − 32) × 5/9 + 273.15
For example, 32°F equals 273.15 K.
7. How do I convert Kelvin to Fahrenheit?
Use:
°F = (K − 273.15) × 9/5 + 32
For example, 300 K is approximately 80.33°F.
8. Can Celsius temperatures be negative?
Yes. Temperatures below 0°C are completely valid. For example, -10°C equals 14°F and 263.15 K.
9. Can Kelvin be negative?
No. Kelvin is an absolute temperature scale, and temperatures below 0 K are not permitted in the conventional thermodynamic temperature scale.
10. What temperature is the same in Celsius and Fahrenheit?
-40 degrees is the unique temperature where the numerical values are the same:
-40°C = -40°F
11. Is 100°C equal to 212°F?
Yes, under standard atmospheric pressure:
100°C = 212°F
This is the commonly recognized boiling point of water at standard atmospheric pressure.
12. Is 0°C equal to 273.15 K?
Yes:
0°C = 273.15 K
The Celsius and Kelvin scales differ by an offset of 273.15.
13. What is normal room temperature in Fahrenheit?
A commonly encountered room-temperature range of approximately 20–25°C corresponds to about 68–77°F. Preferred indoor temperature varies depending on personal comfort and circumstances.
14. Why is Kelvin used instead of Celsius in science?
Kelvin is an absolute temperature scale, making it particularly useful in scientific and thermodynamic equations where temperature must be measured relative to absolute zero.
15. How accurate is a temperature conversion calculator?
The mathematical conversion itself can be highly precise when the appropriate formula is used. The practical accuracy of a displayed result also depends on how many decimal places are retained and how the original temperature was measured.
Final Thoughts
Temperature conversion becomes much easier when you understand how Celsius, Fahrenheit, and Kelvin are related. Each scale serves a different purpose, but all three can describe the same physical temperature.
The key formulas are:
Celsius to Fahrenheit:
°F = (°C × 9/5) + 32
Fahrenheit to Celsius:
°C = (°F − 32) × 5/9
Celsius to Kelvin:
K = °C + 273.15
Kelvin to Celsius:
°C = K − 273.15
Fahrenheit to Kelvin:
K = (°F − 32) × 5/9 + 273.15
Kelvin to Fahrenheit:
°F = (K − 273.15) × 9/5 + 32
The Degree Conversion Calculator provides a convenient way to apply these formulas without doing the arithmetic manually. It is useful for everyday temperature comparisons as well as educational, scientific, engineering, cooking, weather, and technical applications.
By selecting the correct starting unit and target unit, you can quickly determine the equivalent temperature in Celsius, Fahrenheit, or Kelvin. Understanding the formulas behind the results also makes it easier to verify calculations and avoid common conversion mistakes.