Temperature Conversion
Temperature Conversion Formulas
Celsius ↔ Fahrenheit
°F = (°C × 9/5) + 32
°C = (°F - 32) × 5/9
Most common conversion for daily use and cookingCelsius ↔ Kelvin
K = °C + 273.15
°C = K - 273.15
Essential for scientific calculations and thermodynamicsFahrenheit ↔ Kelvin
K = (°F - 32) × 5/9 + 273.15
°F = (K - 273.15) × 9/5 + 32
Direct conversion for engineering applicationsRankine Conversions
°R = °F + 459.67
°R = K × 9/5
°R = (°C + 273.15) × 9/5
Absolute temperature scale used in engineering thermodynamicsReference Temperature Values
| Reference Point | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) | Rankine (°R) |
|---|---|---|---|---|
| Absolute Zero | -273.15 | -459.67 | 0.00 | 0.00 |
| Liquid Nitrogen Boiling | -195.79 | -320.42 | 77.36 | 139.25 |
| Dry Ice Sublimation | -78.50 | -109.30 | 194.65 | 350.37 |
| Water Freezing | 0.00 | 32.00 | 273.15 | 491.67 |
| Human Body Temperature | 37.00 | 98.60 | 310.15 | 558.27 |
| Water Boiling (1 atm) | 100.00 | 212.00 | 373.15 | 671.67 |
| Lead Melting Point | 327.46 | 621.43 | 600.61 | 1081.10 |
| Iron Melting Point | 1538.00 | 2800.40 | 1811.15 | 3260.07 |
| Sun's Surface | 5505.00 | 9941.00 | 5778.15 | 10400.67 |
Temperature Scale Definitions
Celsius (°C) - Metric Standard
Based on the freezing point (0°C) and boiling point (100°C) of water at standard atmospheric pressure (1 atm).
Created by: Anders Celsius (1742), originally inverted from current scale
Zero Point: Freezing point of water under standard conditions
Scale Division: 1°C = 1 K (same magnitude)
Usage: Global standard for meteorology, medicine, and general scientific use
Precision: Typically measured to 0.1°C in practical applications
Fahrenheit (°F) - Imperial Standard
Scale where water freezes at 32°F and boils at 212°F at standard atmospheric pressure.
Created by: Daniel Gabriel Fahrenheit (1724)
Zero Point: Originally based on the lowest temperature achieved with a salt-ice mixture
Scale Division: 180 degrees between freezing and boiling points of water
Usage: Primarily United States, Bahamas, Cayman Islands, and some industrial processes
Human Reference: Body temperature ≈ 98.6°F, making it intuitive for weather
Kelvin (K) - Absolute Temperature
Absolute thermodynamic temperature scale starting at absolute zero, where all molecular motion ceases.
Created by: William Thomson (Lord Kelvin) (1848)
Zero Point: Absolute zero (-273.15°C), theoretical lowest possible temperature
Scale Division: Same magnitude as Celsius degree
Usage: SI base unit, essential for thermodynamics, physics, and chemistry
Critical Points: Triple point of water = 273.16 K (exact definition)
Rankine (°R) - Absolute Fahrenheit
Absolute temperature scale with degree magnitudes equal to Fahrenheit degrees.
Created by: William John Macquorn Rankine (1859)
Zero Point: Absolute zero (same as Kelvin scale)
Scale Division: Same magnitude as Fahrenheit degree
Usage: Engineering applications, particularly in the United States
Relationship: °R = K × 9/5 = °F + 459.67
Scientific Applications
Thermodynamics
Heat Engines: Carnot efficiency η = 1 - T_cold/T_hot (temperatures in Kelvin)
Entropy Changes: ΔS = Q/T for reversible processes
Phase Transitions: Critical for melting, boiling, and sublimation calculations
Chemical Kinetics
Arrhenius Equation: k = Ae^(-Ea/RT)
Reaction Rates: Rule of thumb: Multiple chemical reactions rates double every 10°C temperature increase
Catalyst Performance: Temperature optimization for industrial processes
Materials Science
Thermal Expansion: ΔL = αL₀ΔT
Phase Diagrams: Temperature-dependent material properties
Heat Treatment: Annealing, quenching, and tempering processes
Meteorology & Climate
Heat Index: Apparent temperature combining air temperature and humidity
Atmospheric Modeling: Temperature gradients and pressure relationships
Climate Data: Long-term temperature trend analysis
Food Science
Food Safety: Pathogen kill temperatures and time-temperature relationships
Cooking Science: Protein denaturation and Maillard reactions
Preservation: Pasteurization and sterilization temperature requirements
Medical Applications
Body Temperature: Normal range 36.1-37.2°C (97-99°F)
Hypothermia/Hyperthermia: Critical temperature thresholds
Equipment Sterilization: Autoclave temperatures (121°C minimum)
Measurement Considerations
Absolute vs Relative Scales
Absolute Scales (K, °R): Start at absolute zero, essential for thermodynamic calculations
Relative Scales (°C, °F): Based on arbitrary reference points, suitable for everyday use
Critical for: Gas laws, entropy calculations, and energy transfer equations
Measurement Precision
Thermal Equilibrium: Allow sufficient time for accurate readings
Sensor Placement: Avoid direct radiation, drafts, and conduction effects
Calibration: Regular calibration against known reference standards
Scale Selection Guidelines
Scientific Research: Use Kelvin for thermodynamic calculations
Engineering (US): Rankine for absolute temperatures, Fahrenheit for relative
International Use: Celsius for most applications, Kelvin for scientific work
Cooking: Recipe units (usually Fahrenheit in US, Celsius elsewhere)
Fundamental Temperature Equations
Thermal Energy Transfer
Q = mcΔT
Where: Q = heat energy, m = mass, c = specific heat capacity, ΔT = temperature changeNewton's Law of Cooling
dT/dt = -k(T - T_ambient)
Where: k = heat absorption constant, T = object temperature, T_ambient = ambient temperatureStefan-Boltzmann Law
P = εσAT⁴
Where: P = radiated power, ε = emissivity, σ = Stefan-Boltzmann constant, A = area, T = absolute temperatureGay-Lussac's Law
P₁/T₁ = P₂/T₂ (at constant volume)
Where: P₁, P₂ = pressure values, T₁, T₂ = Temperature values