Throughout the world, there are many different units of measuring temperature. The three most important ones are Fahrenheit (F), Kelvin (K), and Celsius (C). 

Key Facts & Summary

• Celsius and Fahrenheit are degree scales. The degree symbol is not used to report temperature using the Kelvin scale, instead, they are noted as Kelvins.
• Water boils at 100 degrees Celsius or 212 degrees Fahrenheit, or 373.15 Kelvins.
• Water freezes at 0 degrees Celsius or 32 Degrees Fahrenheit, or 273.15 Kelvins.
• Absolute zero is 0 Kelvins. This is the lowest temperature any substance can drop down to.
• Celsius and Fahrenheit are the same at – 40 degrees since the scales converge.
• Celsius and Kelvins become equal at high temperatures as the difference of 273.15 between them gets lost in the noise.
• 0 degrees Celsius is equal to 32 degrees Fahrenheit. The basic formula is (°C × 9/5) + 32 = °F.
• 0 degrees Celsius is equal to 273.15 Kelvins. The basic formula is °C + 273.15 = K.
• The basic formula for converting Fahrenheit into Celsius is (°F − 32) × 5/9 = °C.
• To convert Fahrenheit degrees into Kelvins, (°F − 32) × 5/9 + 273.15 = K.
• To convert Kelvins into Celsius degrees, the formula is K − 273.15 = °C, while the formula of converting Kelvins into Fahrenheit degrees is (K − 273.15) × 9/5 + 32 = °F.
• Temperature can be simply defined as a measure of the hotness or coldness of an object.
• Temperature is measured using a thermometer – we observe the effect of temperature on the substance inside it.