Physical Constants Table (CODATA 2022)
The constants that physics and engineering formulas lean on, with the digits exactly as NIST publishes them in the CODATA 2022 adjustment. Several of them, such as the speed of light and the Planck constant, are exact by definition, because the SI units are now defined by fixing their values; constants built only from those, like the molar gas constant and the Faraday constant, are exact as well, although their decimals never end.
Measured constants, such as the gravitational constant G and the electron mass, come with a standard uncertainty, shown beside the value. Click any value to copy it in full, ready to paste into a calculation.
| Quantity | Symbol | Value | Uncertainty | Unit |
|---|---|---|---|---|
| Speed of light in vacuum | c | exact | m s⁻¹ | |
| Planck constant | h | exact | J Hz⁻¹ | |
| Reduced Planck constant | ħ | exact | J s | |
| Elementary charge | e | exact | C | |
| Boltzmann constant | k | exact | J K⁻¹ | |
| Avogadro constant | NA | exact | mol⁻¹ | |
| Molar gas constant | R | exact | J mol⁻¹ K⁻¹ | |
| Faraday constant | F | exact | C mol⁻¹ | |
| Stefan-Boltzmann constant | σ | exact | W m⁻² K⁻⁴ | |
| Wien wavelength displacement law constant | b | exact | m K | |
| Newtonian constant of gravitation | G | 0.000 15 × 10⁻¹¹ | m³ kg⁻¹ s⁻² | |
| Electron mass | me | 0.000 000 0028 × 10⁻³¹ | kg | |
| Proton mass | mp | 0.000 000 000 52 × 10⁻²⁷ | kg | |
| Neutron mass | mn | 0.000 000 000 85 × 10⁻²⁷ | kg | |
| Atomic mass constant | mu | 0.000 000 000 52 × 10⁻²⁷ | kg | |
| Vacuum electric permittivity | ε₀ | 0.000 000 0014 × 10⁻¹² | F m⁻¹ | |
| Vacuum mag. permeability | μ₀ | 0.000 000 000 20 × 10⁻⁶ | N A⁻² | |
| Fine-structure constant | α | 0.000 000 0011 × 10⁻³ | ||
| Rydberg constant | R∞ | 0.000 012 | m⁻¹ | |
| Bohr radius | a₀ | 0.000 000 000 82 × 10⁻¹¹ | m | |
| Electron volt | eV | exact | J | |
| Molar volume of ideal gas (273.15 K, 101.325 kPa) | Vm | exact | m³ mol⁻¹ | |
| Standard acceleration of gravity | gn | exact | m s⁻² | |
| Standard atmosphere | atm | exact | Pa |
Click a value to copy it.
Values: CODATA 2022, copied from the NIST constants list. "exact" means a defined value, with no uncertainty; "…" means the digits go on.
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