Temperature Conversion Calculator & Table

This temperature conversion calculator instantly converts between Celsius, Fahrenheit, and Kelvin. You enter a temperature value and select the unit you have, and the calculator returns the equivalent in the other two scales, along with a quick-reference table for common temperatures.

Formula

The conversion between temperature scales uses these exact relationships:

• 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

All variables are temperatures: °C in degrees Celsius, °F in degrees Fahrenheit, and K in kelvin (no degree symbol for Kelvin). The formulas are linear, so any temperature can be converted directly without needing a table.

Worked Example

Using the default values from the calculator: convert 100 °C to Fahrenheit and Kelvin.

1. Fahrenheit: °F = (100 × 9/5) + 32 = 180 + 32 = 212 °F
2. Kelvin: K = 100 + 273.15 = 373.15 K

The calculator shows 212.00 °F and 373.15 K, matching these results. Notice that 100 °C is the boiling point of water at standard atmospheric pressure, so 212 °F and 373.15 K are the same physical temperature.

Why Use a Temperature Conversion Table?

While the formulas are simple, a conversion table is handy when you need to check many values quickly or when you are working with temperatures you encounter in daily life. For example, a cook following a recipe from another country might need to convert oven temperatures, or a scientist might need to compare data recorded in different units. A table gives instant reference without mental math, and it helps you spot patterns like the fact that −40 is the same in both Celsius and Fahrenheit.

Here is a short reference table of common temperatures:

• Absolute zero: −273.15 °C, −459.67 °F, 0 K
• Freezing point of water: 0 °C, 32 °F, 273.15 K
• Room temperature (typical): 20–22 °C, 68–72 °F, 293–295 K
• Normal human body temperature: 37 °C, 98.6 °F, 310.15 K
• Boiling point of water: 100 °C, 212 °F, 373.15 K

These are anchor points that help you estimate conversions without a calculator. For instance, knowing that 0 °C is 32 °F and each 5 °C step equals 9 °F lets you approximate: 20 °C is about 68 °F (20 × 9/5 + 32 = 68).

How to Choose the Right Scale

The three main temperature scales serve different purposes:

• Celsius (°C) is used worldwide for everyday weather, cooking, and most scientific work. It is part of the metric system, with 0 °C as the freezing point of water and 100 °C as the boiling point.
• Fahrenheit (°F) is primarily used in the United States for weather, cooking, and body temperature. It has 32 °F as the freezing point and 212 °F as the boiling point of water, giving 180 degrees between them.
• Kelvin (K) is the SI base unit for temperature, used in physics and chemistry. It starts at absolute zero (0 K) and has the same degree size as Celsius, so a change of 1 K equals a change of 1 °C.

Choose the scale based on your context: if you are reading a weather forecast in the US, use Fahrenheit; if you are doing a chemistry experiment, use Kelvin; for most other everyday situations, Celsius is the standard. When converting, always be clear which unit you are starting from.

Common Mistakes and Misconceptions

One frequent error is forgetting to add 32 when converting from Celsius to Fahrenheit. For example, 20 °C is not 36 °F (which is 20 × 9/5 = 36); it is actually 68 °F. Another mistake is using the wrong formula direction: to convert Fahrenheit to Celsius, you must subtract 32 first, then multiply by 5/9. Doing the operations in the wrong order gives a wildly incorrect result.

A common misconception is that Kelvin uses degrees. It does not – you write 300 K, not 300°K. Also, Kelvin is an absolute scale, so it has no negative numbers; the lowest possible temperature is 0 K. In contrast, Celsius and Fahrenheit can be negative.

When rounding, keep enough significant figures for your purpose. For cooking, rounding to the nearest degree is fine, but for scientific work you may need two decimal places. Also, remember that the conversion formulas are exact, so any rounding is only for presentation.

Limits of the Conversion Formula

The linear formulas work for all temperatures, but they assume you are converting between the three standard scales. There are other temperature units, such as Rankine (used in some engineering fields), which have different zero points and degree sizes. The formulas here do not apply to Rankine directly. Also, the physical meaning of temperature – such as the boiling point of water – depends on pressure. At higher altitudes, water boils at a lower temperature, but the conversion between scales remains the same.

For extreme temperatures, like those near absolute zero or in stellar interiors, the same formulas still apply, but the practical measurement may require special instruments. The conversion itself is always valid because it is a mathematical relationship, not a physical law that changes.

Alternatives to a Conversion Table

Besides a table, you can use:

• Mental math: For quick estimates, remember that 0 °C = 32 °F and each 5 °C = 9 °F. So 10 °C ≈ 50 °F, 20 °C ≈ 68 °F, 30 °C ≈ 86 °F.
• Online calculators: This page and many others provide instant conversion with high precision.
• Smartphone apps: Many weather and unit converter apps include temperature conversion built in.
• Physical conversion charts: Printed cards or posters often show common temperatures side by side.

Each method has its place: mental math for rough estimates, a table for repeated reference, and a calculator for precise values. For most people, a simple table covers the temperatures they encounter in daily life, but the formulas give you the exact value for any number.

Frequently Asked Questions

What is the formula to convert Fahrenheit to Celsius?

Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example, 98.6 °F becomes (98.6 − 32) × 5/9 = 37 °C. This is the standard formula used in all scientific and everyday conversions.

Why does −40° equal in both Celsius and Fahrenheit?

Because the two scales intersect at that point. The conversion formula gives (−40 × 9/5) + 32 = −40, and (−40 − 32) × 5/9 = −40. It is the only temperature where the numerical value is the same in both scales.

How do I convert Kelvin to Fahrenheit?

First convert Kelvin to Celsius by subtracting 273.15, then multiply by 9/5 and add 32. For example, 300 K → (300 − 273.15) × 9/5 + 32 = 80.33 °F. You can also use the combined formula: (K − 273.15) × 9/5 + 32.

Is there a temperature where Celsius and Fahrenheit are the same?

Yes, at −40 degrees. This is a well-known mathematical coincidence, not a physical property. It comes from solving the equation C = (C × 9/5) + 32, which gives C = −40.

What is the difference between Celsius and Kelvin?

They have the same degree size, so a change of 1 °C equals a change of 1 K. The difference is the zero point: Celsius sets 0 °C at the freezing point of water, while Kelvin sets 0 K at absolute zero (−273.15 °C). To convert, add or subtract 273.15.

Why do some countries use Fahrenheit and others Celsius?

Historically, Fahrenheit was developed earlier and became standard in English-speaking countries, while Celsius (originally called centigrade) was adopted with the metric system. Today, most of the world uses Celsius, but the US, its territories, and a few other places still use Fahrenheit for everyday purposes.

Related

• Cubic Yard Estimate Calculator: How It Works
• Cubic Yard Calculator: How Much Material You Need
• Cubic Yard Calculator Symbol? Meaning & Use

in t | Temperature | °C | 100 | 0
in from | From unit | °C=1, °F=2, K=3 | 1 | 0
out c | Celsius | °C | if(from==1,t, (from==2,(t-32)*5/9, t-273.15)) | 2
out f | Fahrenheit | °F | if(from==1,t*9/5+32, (from==2,t, (t-273.15)*9/5+32)) | 2
out k | Kelvin | K | if(from==1,t+273.15, (from==2,(t-32)*5/9+273.15, t)) | 2