Speed of light
c = 299792458 m/s
Exact vacuum light speed.
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Constants & Formula Lookup
Searchable reference for major physics constants and formulas, with copy buttons and quick variable definitions.
Constants
Planck constant
h = 6.62607015e-34 J·s
Quantum of action.
Reduced Planck constant
\hbar = 1.054571817e-34 J·s
h divided by 2π.
Elementary charge
e = 1.602176634e-19 C
Charge of a proton in magnitude.
Boltzmann constant
k_B = 1.380649e-23 J/K
Connects temperature and energy.
Avogadro constant
N_A = 6.02214076e23 mol^-1
Entities per mole.
Gas constant
R = 8.314462618 J/(mol·K)
Ideal gas constant.
Gravitational constant
G = 6.6743e-11 N·m²/kg²
Newtonian gravitation constant.
Electron mass
m_e = 9.1093837015e-31 kg
Rest mass of the electron.
Proton mass
m_p = 1.67262192369e-27 kg
Rest mass of the proton.
Neutron mass
m_n = 1.67492749804e-27 kg
Rest mass of the neutron.
Vacuum permittivity
\varepsilon_0 = 8.8541878128e-12 F/m
Electric constant.
Vacuum permeability
\mu_0 = 1.25663706212e-6 N/A²
Magnetic constant.
Coulomb constant
k_e = 8.9875517923e9 N·m²/C²
Appears in Coulomb's law.
Standard gravity
g_0 = 9.80665 m/s²
Standard terrestrial gravity.
Stefan-Boltzmann constant
\sigma = 5.670374419e-8 W/(m²·K⁴)
Blackbody radiation constant.
Rydberg constant
R_\infty = 10973731.56816 m^-1
Hydrogen spectral constant.
Atomic mass constant
u = 1.6605390666e-27 kg
One dalton in SI units.
Formulas
Final velocity in constant acceleration.
v final velocity, v0 initial velocity, a acceleration, t time
Position under constant acceleration.
x final position, x0 initial position, v0 initial velocity, a acceleration, t time
Velocity-displacement relation.
vf final velocity, v0 initial velocity, a acceleration, Δx displacement
Newton's second law.
F net force, m mass, a acceleration
Work by a constant force at angle θ.
W work, F force, d displacement, θ angle
Kinetic energy of a moving body.
K kinetic energy, m mass, v speed
Gravitational potential energy near Earth.
Ug potential energy, m mass, g gravity, h height
Spring potential energy.
Us spring energy, k spring constant, x displacement
Linear momentum.
p momentum, m mass, v velocity
Impulse equals momentum change.
J impulse, Δp momentum change
Ohm's law.
V voltage, I current, R resistance
Electrical power.
P power, I current, V voltage
Coulomb force magnitude.
F force, q charges, r separation
Electric field from force per unit charge.
E electric field, F force, q test charge
Field of a point charge.
E electric field, q charge, r distance
Wave speed relation.
λ wavelength, f frequency, v speed
Snell's law.
n refractive index, θ angle
Ideal gas law.
P pressure, V volume, n moles, R gas constant, T temperature
Photon energy.
E energy, h Planck constant, f frequency
de Broglie wavelength.
λ wavelength, h Planck constant, p momentum