Temperature Conversion
Celsius, Fahrenheit, and Kelvin
Required Parameters
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Quick Answer
°F = (°C × 9/5) + 32. °C = (°F - 32) × 5/9. K = °C + 273.15. The scales cross at -40° (where °C = °F). Water freezes at 0°C / 32°F / 273.15K and boils at 100°C / 212°F / 373.15K.
Design Notes
Electronics datasheets use Celsius exclusively. Standard operating ranges: commercial (0-70°C), industrial (-40 to 85°C), automotive (-40 to 125°C). Junction temperature is the most critical thermal parameter for IC reliability.
Common Mistakes
- 1
Forgetting the offset in Celsius-Fahrenheit conversion — it is NOT a simple multiplication.
- 2
Using ° symbol with Kelvin — correct notation is simply K, not °K.
- 3
Confusing temperature difference with absolute temperature — a 10°C rise = 18°F rise, but 10°C = 50°F.
Knowledge Base
What is 0 Kelvin?
Absolute zero, the lowest possible temperature: 0 K = -273.15 °C = -459.67 °F. At absolute zero, atoms have minimum thermal energy. It is physically impossible to reach exactly 0 K, though scientists have cooled matter to within billionths of a degree.
How do I convert Celsius to Fahrenheit?
°F = (°C × 9/5) + 32. Example: 100°C = (100 × 1.8) + 32 = 212°F. Quick mental math: double the Celsius value and add 30 (accurate within ±2°F for everyday temperatures). Key points: 0°C = 32°F, 37°C = 98.6°F, 100°C = 212°F.
How do I convert Fahrenheit to Celsius?
°C = (°F - 32) × 5/9. Example: 72°F = (72 - 32) × 5/9 = 40 × 0.556 = 22.2°C. Quick mental math: subtract 30 and divide by 2 (rough estimate). 72°F ≈ (72-30)/2 = 21°C (actual: 22.2°C).
What is the relationship between Celsius and Kelvin?
K = °C + 273.15. The scales have the same degree size, just different zero points. Kelvin starts at absolute zero; Celsius starts at the freezing point of water. 0°C = 273.15 K, 100°C = 373.15 K. Kelvin never uses the degree symbol (°).
At what temperature are Fahrenheit and Celsius equal?
At -40°. This is the unique crossover point: -40°C = -40°F. You can derive this by setting °F = °C in the conversion formula: C = (C × 9/5) + 32, solving gives C = -40.
What temperature scale is used in electronics?
Datasheets use Celsius (°C) almost exclusively for operating temperature ranges, junction temperatures, and thermal specifications. Common ratings: commercial (0 to 70°C), industrial (-40 to 85°C), automotive (-40 to 125°C), military (-55 to 125°C). Kelvin is used in physics and for noise temperature calculations.
What is Rankine?
Rankine (°R) is the absolute scale based on Fahrenheit. °R = °F + 459.67. It is used primarily in US thermodynamic engineering and HVAC calculations. 0°R = absolute zero. Water freezes at 491.67°R and boils at 671.67°R. Rankine is to Fahrenheit what Kelvin is to Celsius.
What is the boiling point of water?
100°C (212°F, 373.15 K) at standard atmospheric pressure (101.325 kPa / 1 atm). The boiling point drops with altitude: at 2000m elevation, water boils at about 93°C (200°F). In a pressure cooker (~2 atm), it reaches ~120°C.
What is room temperature in all scales?
Standard room temperature (NIST): 20°C = 68°F = 293.15 K. Comfortable room temperature range: 20-22°C (68-72°F). Datasheet conditions typically specify 25°C (77°F, 298.15 K) as the reference temperature for component specifications.
What is the maximum junction temperature of common ICs?
Most commercial ICs: 125-150°C maximum junction temperature. Industrial: up to 150°C. Automotive-grade: 150-175°C. Power MOSFETs: 150-175°C. LED chips: 120-150°C. Exceeding T_j(max) causes performance degradation and permanent damage.