Scientific Constants Reference

What this tool does

Scientific Constants Reference lists around twenty widely used physical constants, such as the speed of light, Planck constant, gravitational constant, Avogadro constant and standard gravity, each with its symbol, CODATA-style recommended value, SI unit and a short plain-language description. Search by name, symbol or description, and copy any constant’s full line with one click.

Physics and chemistry coursework constantly reaches for the same handful of constants, but remembering the exact value and unit of, say, the Boltzmann constant or the gravitational constant is not something most people carry around in their head. A quick, searchable reference saves a trip to a textbook appendix or a general web search.

This reference lists around twenty of the most commonly used constants with CODATA-style recommended values, following the SI’s 2019 redefinition where several constants, such as the speed of light, Planck constant, elementary charge, Avogadro constant and Boltzmann constant, are now exact by definition rather than measured quantities. Others, including the gravitational constant and the particle masses, still carry a small measurement uncertainty in their last digits, which is noted where relevant.

How to use Scientific Constants Reference

1. Type a name, symbol or keyword from the description into the search box.
2. Scan the filtered table for the constant you need.
3. Read its Symbol, Value, Unit and short Description.
4. Press the copy icon on any row to copy a ready-to-paste line with the name, symbol, value and unit.
5. Clear the search box to see the full list of constants again.

Tips for better results

• Searching by symbol, such as typing just "c" or "h", is often faster than typing the full name if you already know the notation.
• Constants marked as exact by SI definition will never change in future refinements of measurement; those with experimental uncertainty, like G, may be revised slightly as measurement techniques improve.
• Double-check unit prefixes carefully when copying a value into a calculation; many of these constants use very small or very large exponents where a misplaced decimal easily changes the answer by orders of magnitude.
• The description column is meant as a quick memory aid, not a full derivation; pair it with your textbook for the underlying physics.

Common use cases

• Looking up the correct value and unit of a physical constant while solving a physics or chemistry problem.
• Double-checking a constant’s value and SI unit before using it in a lab report or calculation.
• Teaching or reviewing which constants are exact by SI definition versus experimentally measured.
• Quickly copying a constant’s value and unit into notes or a spreadsheet.

Common mistakes to avoid

• Treating every listed constant as having the same level of certainty; several are exact by definition while others, like the gravitational constant, still carry real measurement uncertainty.
• Confusing similarly named constants, such as the Planck constant h and the reduced Planck constant ħ, which differ by a factor of 2π and are used in different contexts.
• Copying a value without its unit into a calculation, since several of these constants are only meaningful paired with their specific SI unit.