Physical Constants

Speed of light in vacuum (c)

299,792,458 m/s

Exact, by definition

Planck constant (h)

6.62607015 × 10⁻³⁴ J·s

Exact, by definition

Elementary charge (e)

1.602176634 × 10⁻¹⁹ C

Exact, by definition

Avogadro constant (Nₐ)

6.02214076 × 10²³ mol⁻¹

Exact, by definition

Boltzmann constant (k)

1.380649 × 10⁻²³ J/K

Exact, by definition

Gas constant (R)

8.314462618 J/(mol·K)

Derived from k and Nₐ

Newtonian gravitational constant (G)

6.67430 × 10⁻¹¹ m³/(kg·s²)

Measured, has uncertainty

Standard gravity (g)

9.80665 m/s²

Exact, by definition

Electron mass (mₑ)

9.1093837015 × 10⁻³¹ kg

Measured

Proton mass (mₚ)

1.67262192369 × 10⁻²⁷ kg

Measured

Vacuum permittivity (ε₀)

8.8541878128 × 10⁻¹² F/m

Measured