Temperature Conversions Explained

Quick answer

Temperature conversions are about moving between different temperature scales, most commonly Fahrenheit (°F), Celsius (°C), and Kelvin (K). Each scale measures temperature, but they use different reference points and intervals.

Most common conversions:
°C = (°F − 32) × 5 ÷ 9
°F = (°C × 9 ÷ 5) + 32
K = °C + 273.15

Fahrenheit

Used mainly in the United States for weather, ovens, and everyday temperature readings.

Celsius

Used in most countries and in science for everyday temperature reporting.

In this guide

Why there are different temperature scales How Fahrenheit works How Celsius works How Kelvin works Temperature conversion formulas Worked examples Common reference temperatures Common conversion mistakes

Why there are different temperature scales

Different temperature scales were developed for different purposes and in different places. Over time, some became standard for daily life, while others became standard for science.

Fahrenheit is common in U.S. daily life.
Celsius is common in international weather and general measurements.
Kelvin is used in science because it starts at absolute zero.

All three scales measure temperature, but they do not use the same zero point or the same spacing between degrees.

How Fahrenheit works

Fahrenheit is often used in the United States for weather forecasts, thermostat settings, and cooking. In this scale:

Water freezes at 32°F
Water boils at 212°F

That means there are 180 Fahrenheit degrees between freezing and boiling.

Quick feel for Fahrenheit:
Around 68°F feels like room temperature, and around 98.6°F is normal body temperature.

How Celsius works

Celsius is simpler for many everyday and scientific uses because it lines up neatly with water’s phase changes:

Water freezes at 0°C
Water boils at 100°C

That gives 100 Celsius degrees between freezing and boiling. Because the number system is clean and easy to remember, Celsius is the most common everyday temperature scale around the world.

How Kelvin works

Kelvin is mainly used in science. It uses the same size interval as Celsius, but the starting point is different.

0 K is absolute zero
273.15 K equals 0°C

Because Kelvin starts at absolute zero, it avoids negative values for many scientific temperature calculations.

Important:
Kelvin is written as K, not °K.

Temperature conversion formulas

Fahrenheit to Celsius

°C = (°F − 32) × 5 ÷ 9

Celsius to Fahrenheit

°F = (°C × 9 ÷ 5) + 32

Celsius to Kelvin

K = °C + 273.15

Kelvin to Celsius

°C = K − 273.15

Fahrenheit to Kelvin

K = (°F − 32) × 5 ÷ 9 + 273.15

Worked examples

Example 1: 68°F to Celsius

Start with the Fahrenheit-to-Celsius formula:

°C = (68 − 32) × 5 ÷ 9

First subtract 32:

68 − 32 = 36

Then multiply by 5 and divide by 9:

36 × 5 ÷ 9 = 20

Result: 68°F = 20°C

Example 2: 100°C to Fahrenheit

°F = (100 × 9 ÷ 5) + 32

Multiply first:

100 × 9 ÷ 5 = 180

Then add 32:

180 + 32 = 212

Result: 100°C = 212°F

Example 3: 25°C to Kelvin

K = 25 + 273.15 = 298.15 K

Common reference temperatures

Freezing point of water

32°F = 0°C = 273.15 K

Boiling point of water

212°F = 100°C = 373.15 K

Room temperature

68°F = 20°C = 293.15 K

Body temperature

98.6°F = 37°C = 310.15 K

Common conversion mistakes

Forgetting to subtract 32 when converting Fahrenheit to Celsius
Adding 273.15 to Fahrenheit directly instead of converting to Celsius first
Mixing up whether to multiply by 5/9 or 9/5
Writing Kelvin with a degree symbol
Rounding too early in a multi-step calculation

Good habit:
Do the full formula first, then round the final result.

Bottom line

Temperature conversions are easy once you know which scale you are starting with and which scale you want to reach. Fahrenheit is common in U.S. daily life, Celsius is common worldwide, and Kelvin is the scientific temperature scale.

Most important formula to remember:
°C = (°F − 32) × 5 ÷ 9