Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin with precise thermodynamic formulas.
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Value
Result
Celsius:
Fahrenheit:
Kelvin:
About Temperature Converter
This temperature converter performs conversions between Celsius (°C), Fahrenheit (°F), and Kelvin (K) using standard thermodynamic formulas. The tool applies the exact conversion constants defined by the International Bureau of Weights and Measures (BIPM) for scientific accuracy.
It is useful for scientific calculations, engineering applications, weather data analysis, cooking temperature conversions, HVAC system design, medical temperature monitoring, chemistry lab work, and educational demonstrations of thermodynamic principles.
Temperature Conversion Formulas
The three temperature scales use these exact conversion formulas:
Celsius ↔ Fahrenheit: F = C × 9/5 + 32 C = (F - 32) × 5/9 Celsius ↔ Kelvin: K = C + 273.15 C = K - 273.15 Fahrenheit ↔ Kelvin: K = (F - 32) × 5/9 + 273.15 F = (K - 273.15) × 9/5 + 32
Key Temperature Reference Points
| Physical Point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute Zero | -273.15°C | -459.67°F | 0 K |
| Water Freezing Point | 0°C | 32°F | 273.15 K |
| Water Triple Point | 0.01°C | 32.018°F | 273.16 K |
| Human Body Temperature | 37°C | 98.6°F | 310.15 K |
| Water Boiling Point (1 atm) | 100°C | 212°F | 373.15 K |
| Equal C/F Point | -40°C | -40°F | 233.15 K |
Temperature Scale Comparison
| Property | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Symbol | °C | °F | K (no degree symbol) |
| Zero Point | Water freezing | Brine mixture (historical) | Absolute zero |
| Scale Interval | 1/100 of water range | 1/180 of water range | Same as Celsius |
| SI Unit | No (derived) | No | Yes (base unit) |
| Primary Usage | Worldwide, science | USA, some territories | Scientific thermodynamics |
Common Temperature Conversions
Weather Temperatures: -40°C = -40°F (extreme cold) -18°C = 0°F (freezer temperature) 0°C = 32°F (freezing point) 10°C = 50°F (cool day) 20°C = 68°F (room temperature) 25°C = 77°F (warm day) 37°C = 98.6°F (body temperature) 40°C = 104°F (hot day) Cooking Temperatures: 100°C = 212°F (water boils) 160°C = 320°F (baking) 180°C = 356°F (moderate oven) 200°C = 392°F (hot oven) 220°C = 428°F (very hot oven) Scientific Temperatures: 0 K = -273.15°C = -459.67°F (absolute zero) 77 K = -196.15°C = -321.07°F (liquid nitrogen) 273.15 K = 0°C = 32°F (water freezes) 293.15 K = 20°C = 68°F (standard lab temp) 373.15 K = 100°C = 212°F (water boils)
Temperature in Different Contexts
| Domain | Typical Range | Preferred Scale |
|---|---|---|
| Meteorology | -50°C to 50°C | Celsius (global), Fahrenheit (US) |
| Medicine | 35°C to 42°C (body) | Celsius (global), Fahrenheit (US) |
| Physics | 0 K to 10^9 K | Kelvin |
| Chemistry | 77 K to 1500 K | Kelvin (calculations), Celsius (lab) |
| Cooking | -18°C to 260°C | Celsius (metric), Fahrenheit (US) |
| HVAC | 10°C to 30°C (indoor) | Celsius (global), Fahrenheit (US) |
Temperature Conversion Examples
Example 1: Convert 25°C to Fahrenheit F = 25 × 9/5 + 32 F = 45 + 32 F = 77°F Example 2: Convert 98.6°F to Celsius C = (98.6 - 32) × 5/9 C = 66.6 × 5/9 C = 37°C Example 3: Convert 300 K to Celsius C = 300 - 273.15 C = 26.85°C Example 4: Convert -40°F to Kelvin K = (-40 - 32) × 5/9 + 273.15 K = -72 × 5/9 + 273.15 K = -40 + 273.15 K = 233.15 K
Historical Background
Temperature Scale Origins: Celsius (1742): - Created by Anders Celsius (Swedish astronomer) - Originally 0=boiling, 100=freezing (reversed later) - Based on water phase transitions at 1 atm - Adopted worldwide as metric standard Fahrenheit (1724): - Created by Daniel Gabriel Fahrenheit (German physicist) - 0°F = coldest brine mixture (ice, water, ammonium chloride) - 32°F = water freezing point - 96°F = human body temperature (original scale) - Still used in USA and some Caribbean nations Kelvin (1848): - Created by William Thomson, 1st Baron Kelvin - Based on thermodynamic absolute zero - 0 K = point of minimum molecular energy - Adopted as SI base unit for temperature - Essential for gas laws and thermodynamics
Thermodynamic Equations Requiring Kelvin
These physics and chemistry equations require temperature in Kelvin:
Ideal Gas Law: PV = nRT R = 8.314 J/(mol·K) — requires Kelvin Stefan-Boltzmann Law: P = σAT⁴ σ = 5.67 × 10⁻⁸ W/(m²·K⁴) — requires Kelvin Boltzmann Factor: E = kT k = 1.38 × 10⁻²³ J/K — requires Kelvin Arrhenius Equation: k = A × exp(-Ea/RT) Requires Kelvin for exponential term
Temperature Precision and Rounding
- Weather: Round to nearest whole degree (±0.5°C accuracy)
- Medical: Use one decimal place (±0.1°C for fever detection)
- Scientific: Use appropriate significant figures based on instrument precision
- Cooking: Round to nearest 5°F or 1°C for practical use
- Engineering: Maintain ±0.01°C for thermal calculations
Frequently Asked Questions
- What are the temperature conversion formulas?
- Celsius to Fahrenheit: F = C × 9/5 + 32. Celsius to Kelvin: K = C + 273.15. Fahrenheit to Celsius: C = (F - 32) × 5/9. Fahrenheit to Kelvin: K = (F - 32) × 5/9 + 273.15. Kelvin to Celsius: C = K - 273.15. Kelvin to Fahrenheit: F = (K - 273.15) × 9/5 + 32.
- What is absolute zero?
- Absolute zero is the lowest possible temperature where molecular motion reaches minimum energy. It equals 0 K, -273.15°C, or -459.67°F. The Kelvin scale starts at absolute zero, making it the standard for scientific thermodynamic calculations.
- Why is 273.15 used in conversions?
- The value 273.15 represents the exact offset between Celsius and Kelvin scales. It derives from the triple point of water (0.01°C = 273.16 K) and the definition that 0 K equals -273.15°C. This constant ensures thermodynamic accuracy in scientific calculations.
- When should I use Kelvin vs Celsius?
- Use Kelvin for thermodynamic equations, gas laws (PV=nRT), physics calculations, and astronomy. Use Celsius for weather, cooking, medical applications, and daily life. Kelvin is required when temperature appears in exponential or ratio contexts since it starts at true zero.
- What is the Fahrenheit scale based on?
- Fahrenheit was originally defined using three fixed points: 0°F (brine ice mixture), 32°F (freezing water), and 96°F (human body temperature, later recalibrated to 98.6°F). The scale divides the water freezing-boiling range into 180 degrees (212°F - 32°F = 180°F).
- At what temperature are Celsius and Fahrenheit equal?
- Celsius and Fahrenheit are equal at -40 degrees: -40°C = -40°F. This can be verified algebraically by setting C = F in the conversion formula F = C × 9/5 + 32, solving for C = -40.