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Physical and mathematical constants (NIST CODATA 2018 / 2019 SI redefinition).
Constants§
- ALPHA
- Fine-structure constant α ≈ 1/137
- ALPHA_
INV - Inverse fine-structure constant 1/α
- AMU
- Atomic mass unit / dalton (kg)
- ATM
- Standard atmosphere (Pa) — exact
- AU
- Astronomical unit (m) — exact (IAU 2012)
- BOHR_
MAGNETON - Bohr magneton μ_B (J/T)
- BOHR_
RADIUS - Bohr radius a₀ (m)
- C
- Speed of light in vacuum (m/s) — exact
- CALORIE
- Thermochemical calorie (J)
- CMB_
TEMPERATURE - Cosmic microwave background temperature (K)
- CONDUCTANCE_
QUANTUM - Conductance quantum G₀ = 2e²/h (S)
- E
- Euler’s number (e)
- EARTH_
MASS - Earth mass M⊕ (kg)
- EARTH_
MOON_ DISTANCE - Mean Earth-Moon distance (m)
- EARTH_
RADIUS - Earth mean radius R⊕ (m)
- EPSILON_
0 - Vacuum permittivity ε₀ (F/m)
- EV_
TO_ JOULES - Electron-volt to joules (J/eV) — same value as E_CHARGE
- E_
CHARGE - Elementary charge (C) — exact (2019 SI redefinition)
- FARADAY
- Faraday constant F = N_A × e (C/mol) — exact, and computed from its two exact factors rather than transcribed, so it cannot disagree with them.
- FIRST_
RADIATION - First radiation constant c₁ = 2πhc² (W·m²)
- G
- Gravitational constant (m³ kg⁻¹ s⁻²) — ±0.000_15e-11
- G_ACCEL
- Standard gravitational acceleration (m/s²) — exact by definition
- H
- Planck’s constant (J·s) — exact (2019 SI redefinition)
- HBAR
- Reduced Planck’s constant ℏ = h/(2π) (J·s) — exact
- HUBBLE
- Hubble constant H₀ ≈ 69.8 km/s/Mpc (s⁻¹)
- JOSEPHSON
- Josephson constant K_J = 2e/h (Hz/V)
- K_B
- Boltzmann constant (J/K) — exact (2019 SI redefinition)
- K_E
- Coulomb constant k_e = 1/(4πε₀) (N·m²/C²)
- LIGHT_
YEAR - Light-year (m) — exact
- LN_2
- Natural logarithm of 2
- LN_10
- Natural logarithm of 10
- MAGNETIC_
FLUX_ QUANTUM - Magnetic flux quantum Φ₀ = h/(2e) (Wb)
- MU_0
- Vacuum permeability μ₀ (H/m)
- M_
ELECTRON - Electron mass (kg)
- M_
NEUTRON - Neutron mass (kg)
- M_
PROTON - Proton mass (kg)
- NUCLEAR_
MAGNETON - Nuclear magneton μ_N (J/T)
- N_A
- Avogadro constant (mol⁻¹) — exact (2019 SI redefinition)
- PARSEC
- Parsec (m)
- PI
- Pi (π)
- PLANCK_
CHARGE - Planck charge √(4πε₀ℏc) (C)
- PLANCK_
LENGTH - Planck length √(ℏG/c³) (m)
- PLANCK_
MASS - Planck mass √(ℏc/G) (kg)
- PLANCK_
TEMPERATURE - Planck temperature √(ℏc⁵/(G·k_B²)) (K)
- PLANCK_
TIME - Planck time √(ℏG/c⁵) (s)
- R
- Molar gas constant R = N_A × k_B (J mol⁻¹ K⁻¹) — exact
- RYDBERG
- Rydberg constant R∞ (m⁻¹)
- RYDBERG_
ENERGY - Rydberg energy (J) ≈ 13.6 eV
- SECOND_
RADIATION - Second radiation constant c₂ = hc/k_B (m·K)
- SIGMA
- Stefan-Boltzmann constant σ (W m⁻² K⁻⁴)
- SOLAR_
LUMINOSITY - Solar luminosity L☉ (W)
- SOLAR_
MASS - Solar mass M☉ (kg)
- SOLAR_
RADIUS - Solar radius R☉ (m)
- SOLAR_
TEMPERATURE - Solar effective temperature T☉ (K)
- SQRT_2
- Square root of 2
- TAU
- Tau (2π)
- TORR
- Torr (Pa)
- VACUUM_
IMPEDANCE - Impedance of free space Z₀ = μ₀c (Ω)
- VON_
KLITZING - Von Klitzing constant R_K = h/e² (Ω)
- WIEN_
DISPLACEMENT - Wien displacement law constant b (m·K)