Type a symbol (c, h, k) or part of a name (Planck, Avogadro) to filter the list below.
Reading a physics data sheet without mixing up precision and exactness
Since the 2019 redefinition of the SI, seven constants including the Planck constant h, the elementary charge e, the Boltzmann constant k, and the Avogadro constant are fixed by definition and carry no uncertainty at all. Everything else on this list, such as the Newtonian constant of gravitation G or the electron mass, is a measured value with a stated uncertainty attached to it. Mixing up the two is a common mistake at A-level: a defined constant is exact by convention, a measured one is only known to the precision of the best experiment carried out so far. Search by symbol or name above, or filter by category, to browse all 21 constants with their CODATA value, SI unit, and uncertainty where one applies.
| Category | Typical use |
|---|---|
| Universal | Speed of light, gravitation, Planck constant: apply across all of physics |
| Electromagnetic | Elementary charge, vacuum permittivity: electricity and magnetism |
| Thermodynamic | Boltzmann constant, Avogadro constant, gas constant: heat and matter in bulk |
| Atomic & nuclear | Electron, proton and neutron mass, fine-structure constant: single-particle physics |
Why the exam data booklet shows fewer digits than this page
AQA, OCR, and Edexcel physics data sheets round most constants to three or four significant figures, which is plenty for the calculations set at GCSE and A-level. The values on this page follow the fuller CODATA recommendations instead, since a data reference is more useful with the extra digits included than trimmed to exam-paper length. The speed of light is the one figure worth memorising exactly regardless: 2.99792458 times 10 to the 8 metres per second, fixed by definition rather than measured, which is also why it never appears with an uncertainty attached.
What this reference does not do
This page lists the constants set out in a standard secondary and university physics course, it does not propagate uncertainty through a multi-step calculation, and it does not cover material-specific or astronomical figures such as the mass of the Earth or the solar constant. For the arithmetic side of a physics problem, pair this reference with the Scientific Calculator, or check the Periodic Table Lookup for the atomic mass of a specific element rather than the fixed atomic mass unit listed here.
A note on notation
Values are written in scientific notation as a mantissa multiplied by a power of 10, for example 6.62607015 times 10 to the minus 34 for the Planck constant in joule seconds. This matches the format used on UK exam formula sheets and in most university textbooks, so a value copied from this page should paste directly into a calculator or spreadsheet cell without further editing.