Engineering Constants
Comprehensive reference for physical constants, unit conversion factors, standard atmospheric properties, and derived engineering values used across all disciplines.
Engineering Constants – Physical & Standard Values
Comprehensive reference for physical constants, unit conversion factors, standard atmospheric properties, and common engineering values used across all disciplines.
Why Know Your Constants?
Every engineering calculation is anchored to fundamental physical constants and standard reference values. The universal gas constant R = 8.314 J/(mol·K) underpins thermodynamics; gravitational acceleration g = 9.81 m/s² is used in every statics and dynamics problem; the Stefan-Boltzmann constant governs radiation heat transfer. Having precise, reliable values reduces errors and speeds up calculations.
Constant Categories:
- ⚛️ Physical Constants – g, R, π, σ (Stefan-Boltzmann), k_B (Boltzmann), N_A (Avogadro), c (speed of light), h (Planck).
- 🔧 Unit Conversion Factors – Key multipliers between SI and other systems for mass, force, energy, pressure, and power.
- 🌍 Atmospheric & Water Properties – Standard atmosphere (p₀, T₀, ρ₀), water density, viscosity, and thermal properties at standard conditions.
- 🧮 Derived Engineering Values – Shear modulus relationship G = E/[2(1+ν)], thermal diffusivity α = k/(ρ·c_p), and other derived constants.
Physical Constants Reference
Searchable reference table of 14 fundamental physical and engineering constants. Includes an example Stefan–Boltzmann radiation calculation: Q = ε·σ·A·T⁴.
| Constant | Symbol | Value | Unit | Description |
|---|---|---|---|---|
| Gravitational Acceleration | g | 9.806650 | m/s² | Standard gravity at Earth's surface |
| Universal Gas Constant | R | 8.314460 | J/(mol·K) | Molar gas constant |
| Boltzmann Constant | k_B | 1.380649e-23 | J/K | Thermal energy per degree Kelvin |
| Avogadro's Number | N_A | 6.022141e+23 | mol⁻¹ | Number of entities per mole |
| Stefan–Boltzmann Constant | σ | 5.670370e-8 | W/(m²·K⁴) | Radiant emittance of black body |
| Speed of Light (vacuum) | c | 2.997925e+8 | m/s | Speed of electromagnetic waves |
| Planck Constant | h | 6.626070e-34 | J·s | Quantum of electromagnetic action |
| Permittivity of Free Space | ε₀ | 8.854190e-12 | F/m | Electric constant |
| Permeability of Free Space | μ₀ | 0.000001256640 | H/m | Magnetic constant |
| Faraday Constant | F | 96485.33 | C/mol | Charge per mole of electrons |
| Electron Charge | e | 1.602176e-19 | C | Elementary charge |
| Atmospheric Pressure (std) | P₀ | 101325.0 | Pa | Standard atmosphere at sea level |
| Molar Mass of Air | M_a | 0.02896400 | kg/mol | Dry air |
| Specific Heat of Air (c_p) | c_pa | 1005.000 | J/(kg·K) | Constant pressure, 20°C |