🌡️ Temperature Conversion

Convert between five temperature scales: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), and Réaumur (°Re). The temperature converter uses precise formulas for each scale conversion and includes real-world reference points like freezing point (0°C / 32°F), boiling point (100°C / 212°F), and absolute zero (0 K / -273.15°C).

Temperature conversion calculates thermal equilibrium across Celsius (°C), Fahrenheit (°F), and Kelvin (K). The kelvin and degree Celsius share the exact same interval size, with 0 °C defined as 273.15 K, while 0 °C corresponds exactly to 32 °F by scale conversion relationship. Absolute zero corresponds to 0 K (−273.15 °C). The exact affine formulas are °F = (°C × 9/5) + 32 and K = °C + 273.15.

Metrological Standards & Base Equation

°F = (°C × 9/5) + 32. K = °C + 273.15. °C = (°F − 32) × 5/9.

Thermal conversion algorithms adhere to SI base unit definitions (with the kelvin defined via the Boltzmann constant k = 1.380649 × 10⁻²³ J/K), NIST Special Publication 811, and the BIPM SI Brochure (9th Edition). Fahrenheit and Rankine calculations use exact rational fractions without intermediary rounding.

Primary References: BIPM Measurement Units · NIST SP 811 (2008 Edition) · Standards Directory

Supported Temperature Units (5 Total)

Temperature Unit Definitions and Scaling Factors
Unit Symbol Unit Name System Conversion Basis
°C Celsius Metric Affine temperature scale
°F Fahrenheit Imperial Affine temperature scale
K Kelvin Scientific SI Base Unit (Kelvin)
°R °Rankine Scientific Affine temperature scale
°Ré °Réaumur Other Affine temperature scale

Popular Temperature Conversions

Celsius to Fahrenheit

°C → °F — weather & daily temperature

Fahrenheit to Celsius

°F → °C — international travel

Celsius to Kelvin

°C → K — scientific & chemistry calculations

Kelvin to Celsius

K → °C — physics & engineering

Fahrenheit to Kelvin

°F → K — advanced science

Conversion Guides & Step-by-Step Formulas

Step-by-step formula derivation, worked examples, and quick lookup tables.
Step-by-step formula derivation, worked examples, and quick lookup tables.

Common Use Cases

  • Weather & climate (°C↔°F)
  • Cooking & baking (°C↔°F)
  • Science & chemistry (K↔°C)
  • Engineering & physics (K↔°R)
  • HVAC & refrigeration

Frequently Asked Questions

How do I convert Celsius to Fahrenheit?

Multiply Celsius by 9/5 (1.8) then add 32. For example, 25°C × 1.8 + 32 = 77°F.

What is absolute zero in Celsius?

Absolute zero is 0 Kelvin, which equals -273.15°C or -459.67°F.