Physical Constants
Fundamental physical constants, gas constant conversions, and common unit conversion factors used in chemistry.
Fundamental Constants
| Constant | Symbol | Value | Unit |
|---|---|---|---|
| Speed of light | c | 2.998 × 10⁸ | m/s |
| Planck’s constant | h | 6.626 × 10⁻³⁴ | J·s |
| Reduced Planck constant | ℏ | 1.055 × 10⁻³⁴ | J·s |
| Boltzmann constant | kB | 1.381 × 10⁻²³ | J/K |
| Avogadro’s number | NA | 6.022 × 10²³ | mol⁻¹ |
| Elementary charge | e | 1.602 × 10⁻¹⁹ | C |
| Gas constant | R | 8.314 | J/(mol·K) |
| Faraday constant | F | 96,485 | C/mol |
| Electron mass | mₑ | 9.109 × 10⁻³¹ | kg |
| Proton mass | mₚ | 1.673 × 10⁻²⁷ | kg |
| Neutron mass | mₙ | 1.675 × 10⁻²⁷ | kg |
| Atomic mass unit | u | 1.661 × 10⁻²⁷ | kg |
| Bohr radius | a₀ | 5.292 × 10⁻¹¹ | m |
| Vacuum permittivity | ε₀ | 8.854 × 10⁻¹² | F/m |
| Coulomb constant | kₑ | 8.988 × 10⁹ | N·m²/C² |
Gas Constant in Various Units
| Value | Unit |
|---|---|
| 8.314 | J/(mol·K) |
| 0.08206 | L·atm/(mol·K) |
| 8.314 | Pa·m³/(mol·K) |
| 62.36 | L·mmHg/(mol·K) |
| 1.987 | cal/(mol·K) |
Common Conversion Factors
| Conversion | Value |
|---|---|
| 1 eV | 1.602 × 10⁻¹⁹ J |
| 1 eV | 96.485 kJ/mol |
| 1 cal | 4.184 J |
| 1 atm | 101,325 Pa |
| 1 atm | 760 mmHg |
| 1 Å | 10⁻¹⁰ m = 100 pm |
| 1 amu | 931.5 MeV/c² |
| 0 °C | 273.15 K |
| STP | 273.15 K, 1 atm |
| Molar volume (STP) | 22.414 L/mol |
Related Tools
Values from CODATA 2018 recommended values. For the most precise and up-to-date values, consult the NIST Reference on Constants, Units, and Uncertainty.