Physical constants table — CODATA 2018 values with uncertainties

How to use the physical constants table

1. Type in Search: part of a name (Planck, electron), a symbol (G, R, N_A) or the word “exact”.
2. Narrow the list with Category: Universal, Electromagnetic, Physico-chemical, Atomic and nuclear, or Adopted values.
3. Read the table: quantity, symbol, value with digit groups, Plain number, standard uncertainty and unit.
4. Copy the Plain number (such as 6.62607015e-34) straight into a calculator, spreadsheet or code. The table can also be saved as codata-2018.csv.

What it does and when to use it

Physics and chemistry problems often stop while you hunt for a constant, and a missing digit or a wrong power of ten ruins the answer. This table gives the official value, its unit and its uncertainty in one place. It suits homework, lab reports, and checking the figures on a data sheet.

For the prefixes in units such as MeV or nm, see the SI unit prefix table. The Greek symbols used for constants, such as σ, Φ and ħ, are explained in the Greek alphabet reference. For molar masses, use the molar mass calculator.

How it works

The values were copied from NIST’s CODATA 2018 listing. The table shows each value in groups of three digits, as NIST does, with powers of ten written as × 10ⁿ, and gives the same value as a plain number in E notation. Units use superscripts, so m^3 kg^-1 s^-2 becomes m³ kg⁻¹ s⁻². Search matches part of a name, an exact symbol, or “exact” for defined values. The search runs in your browser.

Worked examples

Avogadro constant. Searching “Avogadro” gives N_A = 6.022 140 76 × 10²³ mol⁻¹, marked exact. Its plain number is 6.02214076e23.

Electron mass. Searching “electron mass” lists four entries: the mass in kilograms, 9.109 383 7015 × 10⁻³¹ kg with an uncertainty of 0.000 000 0028 × 10⁻³¹, the mass in atomic mass units, its energy equivalent of 0.510 998 950 00 MeV, and the proton–electron mass ratio.

Defined values. Searching “exact” returns 26 constants, from the speed of light, 299 792 458 m s⁻¹, to the standard atmosphere, 101 325 Pa.

Limits and tips

• A one-letter search matches every name containing that letter as well as the symbol, so “k” shows the Planck constant too. Use the full name for a short list.
• Round only at the end of a calculation, and give your answer to the same significant figures as your least precise data.
• Exam data sheets often round constants (for example g = 9.81 m s⁻²). Use the values your exam board gives.