Physical Constants
A searchable table of common physics constants with accurate values, symbols, and SI units.
Copy any value with its button.
| Symbol | Name | Value | Units | Copy |
|---|---|---|---|---|
| c | Speed of light | 2.998×10⁸ | m/s | |
| G | Gravitational constant | 6.674×10⁻¹¹ | N·m²/kg² | |
| h | Planck constant | 6.626×10⁻³⁴ | J·s | |
| e | Elementary charge | 1.602×10⁻¹⁹ | C | |
| Nₐ | Avogadro’s number | 6.022×10²³ | /mol | |
| k_B | Boltzmann constant | 1.381×10⁻²³ | J/K | |
| R | Gas constant | 8.314 | J/(mol·K) | |
| mₑ | Electron mass | 9.109×10⁻³¹ | kg | |
| m_p | Proton mass | 1.673×10⁻²⁷ | kg | |
| g | Standard gravity | 9.807 | m/s² | |
| ε₀ | Vacuum permittivity | 8.854×10⁻¹² | F/m | |
| F | Faraday constant | 96485 | C/mol |
Physical constants are fixed quantities of nature that appear in the laws of physics — the same everywhere, every time. Key examples are the speed of light c = 2.998×10⁸ m/s, the gravitational constant G = 6.674×10⁻¹¹ N·m²/kg², and the Planck constant h = 6.626×10⁻³⁴ J·s. Search the table above and copy any value.
What physical constants are
A physical constant is a number that nature seems to fix — it does not depend on where or when you measure it. These constants tie the equations of physics to the real world: c sets the cosmic speed limit and links space to time, G sets the strength of gravity, and h sets the scale of the quantum world. Once you know them, formulas turn into actual numbers.
How to read the table
Each row gives the symbol used in equations, the constant’s name, its value in scientific notation, and its SI units. Values are written as a coefficient times a power of ten (for example 6.022×10²³), which keeps very large and very small numbers readable. Use the search box to filter by name or symbol, and copy a value straight into your own calculation.
Common physical constants
Standard values rounded to four significant figures, expressed in SI units.
| Symbol | Name | Value | Units |
|---|---|---|---|
| c | Speed of light | 2.998×10⁸ | m/s |
| G | Gravitational constant | 6.674×10⁻¹¹ | N·m²/kg² |
| h | Planck constant | 6.626×10⁻³⁴ | J·s |
| e | Elementary charge | 1.602×10⁻¹⁹ | C |
| Nₐ | Avogadro’s number | 6.022×10²³ | /mol |
| k_B | Boltzmann constant | 1.381×10⁻²³ | J/K |
| R | Gas constant | 8.314 | J/(mol·K) |
| mₑ | Electron mass | 9.109×10⁻³¹ | kg |
| m_p | Proton mass | 1.673×10⁻²⁷ | kg |
| g | Standard gravity | 9.807 | m/s² |
| ε₀ | Vacuum permittivity | 8.854×10⁻¹² | F/m |
| F | Faraday constant | 96485 | C/mol |
Where these values come from
The internationally agreed values are published by CODATA, which periodically reviews the best measurements and adjusts the recommended numbers. The values here are rounded to about four significant figures for everyday work; the official figures carry many more digits. Since the 2019 redefinition of the SI, several constants — including c, h, e, Nₐ, and k_B — are defined exactly, fixing the units themselves rather than being measured.
All values are quoted in SI units, so they slot directly into formulas written in metres, kilograms, seconds, and the rest of the SI base units. If your equation uses other units, convert first or your answer will be off by powers of ten. The gas constant R and the Boltzmann constant k_B describe the same physics at different scales — R per mole, k_B per particle — related by R = Nₐ × k_B.