liminfoPhysical Constants Reference
Free web tool: Physical Constants Reference
Showing 24 of 24 constants
| Name | Symbol | Value | Unit |
|---|---|---|---|
| Speed of light in vacuum | c | 2.998 × 10⁸ | m/s |
| Planck constant | h | 6.626 × 10⁻³⁴ | J·s |
| Reduced Planck constant | ℏ | 1.055 × 10⁻³⁴ | J·s |
| Boltzmann constant | k_B | 1.381 × 10⁻²³ | J/K |
| Gravitational constant | G | 6.674 × 10⁻¹¹ | N·m²/kg² |
| Elementary charge | e | 1.602 × 10⁻¹⁹ | C |
| Electron mass | m_e | 9.109 × 10⁻³¹ | kg |
| Proton mass | m_p | 1.673 × 10⁻²⁷ | kg |
| Neutron mass | m_n | 1.675 × 10⁻²⁷ | kg |
| Avogadro constant | N_A | 6.022 × 10²³ | mol⁻¹ |
| Gas constant | R | 8.314 | J/(mol·K) |
| Faraday constant | F | 9.649 × 10⁴ | C/mol |
| Vacuum permittivity | ε₀ | 8.854 × 10⁻¹² | F/m |
| Vacuum permeability | μ₀ | 1.257 × 10⁻⁶ | N/A² |
| Stefan–Boltzmann constant | σ | 5.670 × 10⁻⁸ | W/(m²·K⁴) |
| Coulomb constant | k_e | 8.988 × 10⁹ | N·m²/C² |
| Atomic mass unit | u | 1.661 × 10⁻²⁷ | kg |
| Bohr radius | a₀ | 5.292 × 10⁻¹¹ | m |
| Rydberg constant | R_∞ | 1.097 × 10⁷ | m⁻¹ |
| Fine-structure constant | α | 7.297 × 10⁻³ | dimensionless |
| Magnetic flux quantum | Φ₀ | 2.068 × 10⁻¹⁵ | Wb |
| Wien displacement constant | b | 2.898 × 10⁻³ | m·K |
| Standard gravity | g | 9.807 | m/s² |
| Standard atmosphere | atm | 1.013 × 10⁵ | Pa |
About Physical Constants Reference
The Physical Constants Reference is a searchable table of 24 fundamental constants used across physics, chemistry, and engineering. The collection spans mechanics, thermodynamics, electromagnetism, quantum mechanics, and atomic physics — including the speed of light (c), Planck constant (h), reduced Planck constant (ℏ), Boltzmann constant (k_B), gravitational constant (G), elementary charge (e), electron mass (m_e), proton mass (m_p), Avogadro constant (N_A), and more. Each entry is displayed with its official symbol, a concise scientific notation value, and the SI unit.
This reference is used daily by physics and chemistry students who need quick access to accurate constant values for problem sets, lab reports, and formula verification. Engineering students working on thermodynamics, semiconductor physics, or electromagnetic problems also rely on it to look up constants like vacuum permittivity (ε₀), vacuum permeability (μ₀), Faraday constant (F), Stefan-Boltzmann constant (σ), and the fine-structure constant (α) without having to flip through textbook appendices or memorize them.
The tool is built with a live search bar that filters the list in real time as you type, matching against the constant name, symbol, or unit. The search is powered by a useMemo hook so filtering is instant and never blocks the UI. All 24 constants are stored as a static array in the component, so the page loads instantly, works offline, and never makes a network request. The table is horizontally scrollable for comfortable use on small screens.
Key Features
- Collection of 24 fundamental physical constants across multiple domains of physics
- Live search filtering by name, symbol, or unit — results update as you type
- Scientific notation values (e.g., 2.998 × 10⁸) formatted for readability
- SI units displayed for every constant with proper Unicode symbols (J·s, N·m², C/mol, etc.)
- Covers mechanics, thermodynamics, electromagnetism, quantum, and atomic constants
- Result count displayed so you always know how many constants match your search
- 100% client-side — all constants are embedded in the page, no server calls needed
- Dark mode support and responsive table with horizontal scroll on small screens
Frequently Asked Questions
What physical constants are included in this reference?
The reference includes 24 constants: speed of light (c), Planck constant (h), reduced Planck constant (ℏ), Boltzmann constant (k_B), gravitational constant (G), elementary charge (e), electron mass (m_e), proton mass (m_p), neutron mass (m_n), Avogadro constant (N_A), gas constant (R), Faraday constant (F), vacuum permittivity (ε₀), vacuum permeability (μ₀), Stefan-Boltzmann constant (σ), Coulomb constant (k_e), atomic mass unit (u), Bohr radius (a₀), Rydberg constant (R_∞), fine-structure constant (α), magnetic flux quantum (Φ₀), Wien displacement constant (b), standard gravity (g), and standard atmosphere (atm).
How do I search for a specific constant?
Type any part of the constant name, symbol, or unit into the search bar. For example, typing "planck" finds the Planck constant and reduced Planck constant, typing "J/K" finds constants measured in joules per kelvin, and typing "e" will match the elementary charge symbol.
Are the constant values accurate and up to date?
The values are based on the 2018 CODATA recommended values, which are the internationally accepted standards used in scientific and engineering work. For the most current CODATA values, refer to the NIST physical constants database.
What is the fine-structure constant and why is it dimensionless?
The fine-structure constant (α ≈ 7.297 × 10⁻³, approximately 1/137) describes the strength of the electromagnetic interaction between charged particles. It is a dimensionless pure number because it is formed from the ratio of other fundamental constants (e², ℏ, c) in a way that all physical units cancel out.
What is the difference between the gas constant (R) and the Boltzmann constant (k_B)?
The Boltzmann constant (k_B) applies at the level of individual particles, while the gas constant (R) applies at the level of moles of substances. They are related by R = N_A × k_B, where N_A is Avogadro's number. R appears in the ideal gas law (PV = nRT) and k_B appears in statistical mechanics (E = k_B T).
What is the Bohr radius used for?
The Bohr radius (a₀ ≈ 5.292 × 10⁻¹¹ m) is the most probable distance between the nucleus and the electron in a ground-state hydrogen atom. It is the fundamental length scale of atomic physics and quantum chemistry, used in calculations involving atomic orbitals and the Schrödinger equation for hydrogen.
What is the Wien displacement constant?
The Wien displacement constant (b ≈ 2.898 × 10⁻³ m·K) is used in Wien's displacement law, which states that the peak wavelength of blackbody radiation is inversely proportional to the temperature. It is applied in astrophysics to estimate stellar surface temperatures from observed spectral peak wavelengths.
Can I use this reference offline?
Yes. All constant values are embedded directly in the page JavaScript, so the tool works fully offline once the page has loaded. There are no API calls or external data fetches required at any point.