Fundamental physical constants (CODATA)

Name: Fundamental physical constants (CODATA)
Creator: AIDB
License: https://www.nist.gov/open/license

The internationally recommended values of the fundamental physical constants — the speed of light, Planck constant, electron mass, fine-structure constant and about 350 more — from the latest CODATA adjustment, as published by NIST. One row per constant, with value, standard uncertainty and unit.

355 rows8 columns Updated 1 d ago Facts (not copyrightable) — source credited

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Quantity

Value

Standard uncertainty

Relative uncertainty

Unit

Exact

Angstrom star

1.000e-10

9.000e-17

9.000e-7

Avogadro constant

6.022e+23

0.000e+0

mol^-1

Yes

Bohr magneton

9.274e-24

2.900e-33

3.100e-10

J T^-1

Bohr magneton in Hz/T

1.400e+10

4.400e+0

3.100e-10

Hz T^-1

Bohr magneton in K/T

6.717e-1

2.100e-10

3.100e-10

K T^-1

Bohr magneton in eV/T

5.788e-5

1.800e-14

3.100e-10

eV T^-1

Bohr magneton in inverse meter per tesla

4.669e+1

1.500e-8

3.200e-10

m^-1 T^-1

Bohr radius

5.292e-11

8.200e-21

1.500e-10

Boltzmann constant

1.381e-23

0.000e+0

J K^-1

Yes

Boltzmann constant in Hz/K

2.084e+10

0.000e+0

Hz K^-1

Yes

Boltzmann constant in eV/K

8.617e-5

0.000e+0

eV K^-1

Yes

Boltzmann constant in inverse meter per kelvin

6.950e+1

0.000e+0

m^-1 K^-1

Yes

Compton wavelength

2.426e-12

7.600e-22

3.100e-10

Copper x unit

1.002e-13

2.800e-20

2.800e-7

Faraday constant

9.649e+4

0.000e+0

C mol^-1

Yes

Fermi coupling constant

1.166e-5

6.000e-12

5.100e-7

GeV^-2

Hartree energy

4.360e-18

4.800e-30

1.100e-12

Hartree energy in eV

2.721e+1

3.000e-11

1.100e-12

Josephson constant

4.836e+14

0.000e+0

Hz V^-1

Yes

Loschmidt constant (273.15 K, 100 kPa)

2.652e+25

0.000e+0

m^-3

Yes

Loschmidt constant (273.15 K, 101.325 kPa)

2.687e+25

0.000e+0

m^-3

Yes

Molybdenum x unit

1.002e-13

5.300e-20

5.300e-7

Newtonian constant of gravitation

6.674e-11

1.500e-15

2.200e-5

m^3 kg^-1 s^-2

Newtonian constant of gravitation over h-bar c

6.709e-39

1.500e-43

2.200e-5

(GeV/c^2)^-2

Planck constant

6.626e-34

0.000e+0

J Hz^-1

Yes

Planck constant in eV/Hz

4.136e-15

0.000e+0

eV Hz^-1

Yes

Planck length

1.616e-35

1.800e-40

1.100e-5

Planck mass

2.176e-8

2.400e-13

1.100e-5

Planck mass energy equivalent in GeV

1.221e+19

1.400e+14

1.100e-5

GeV

Planck temperature

1.417e+32

1.600e+27

1.100e-5

Planck time

5.391e-44

6.000e-49

1.100e-5

Rydberg constant

1.097e+7

1.200e-5

1.100e-12

m^-1

Rydberg constant times c in Hz

3.290e+15

3.600e+3

1.100e-12

Rydberg constant times hc in J

2.180e-18

2.400e-30

1.100e-12

Rydberg constant times hc in eV

1.361e+1

1.500e-11

1.100e-12

Sackur-Tetrode constant (1 K, 100 kPa)

-1.152e+0

4.700e-10

4.100e-10

Sackur-Tetrode constant (1 K, 101.325 kPa)

-1.165e+0

4.700e-10

4.000e-10

Stefan-Boltzmann constant

5.670e-8

0.000e+0

W m^-2 K^-4

Yes

Thomson cross section

6.652e-29

6.200e-38

9.300e-10

m^2

W to Z mass ratio

8.814e-1

1.300e-4

1.500e-4

Wien frequency displacement law constant

5.879e+10

0.000e+0

Hz K^-1

Yes

Wien wavelength displacement law constant

2.898e-3

0.000e+0

m K

Yes

alpha particle mass

6.645e-27

2.100e-36

3.200e-10

alpha particle mass energy equivalent

5.972e-10

1.900e-19

3.200e-10

alpha particle mass energy equivalent in MeV

3.727e+3

1.200e-6

3.200e-10

MeV

alpha particle mass in u

4.002e+0

6.200e-11

1.500e-11

alpha particle molar mass

4.002e-3

1.200e-12

3.000e-10

kg mol^-1

alpha particle relative atomic mass

4.002e+0

6.200e-11

1.500e-11

alpha particle rms charge radius

1.678e-15

2.100e-18

1.300e-3

alpha particle-electron mass ratio

7.294e+3

1.700e-7

2.300e-11

Columns

Stable keys — use them in the API, SQL and code

Key	Name	Type	Description
quantity	Quantity	string	—
value	Value	number	Recommended value, as a number.
uncertainty	Standard uncertainty	number	One-sigma standard uncertainty, same unit as the value. Zero for exact constants.
relative_uncertainty	Relative uncertainty	number	Standard uncertainty divided by the absolute value.
unit	Unit	string	SI unit as written by NIST (e.g. m s^-1). Empty for dimensionless constants.
exact	Exact	boolean	True when the value is exact by definition of the SI.
value_text	Value as published	string	Value exactly as printed by NIST, with digit grouping.
uncertainty_text	Uncertainty as published	string	—

About this data

Source: NIST — CODATA Internationally Recommended Values of the Fundamental Physical Constants (complete listing)
License: Facts (not copyrightable) — source credited
Required attribution: CODATA recommended values of the fundamental physical constants, NIST Reference on Constants, Units, and Uncertainty (physics.nist.gov/constants).
Updated: Oct 9, 2026 15:29 UTC
Refresh: yearly
Rows: 355
Size (JSON): 41 KB
Notes: Values are from the most recent CODATA adjustment published by NIST (the file header names the adjustment year; this build used whatever NIST currently serves). Since the 2019 SI redefinition, the speed of light, Planck constant, elementary charge, Boltzmann constant, Avogadro constant and others are exact by definition, so their uncertainty is zero and 'Exact' is true. Some exact values have infinitely many digits; NIST truncates them (shown with '...' in the value as published), and the numeric Value column holds the truncated number. 'Value as published' keeps NIST's exact digits and spacing. Uncertainty is the standard (one-sigma) uncertainty in the same unit; relative uncertainty is computed by AIDB as uncertainty ÷ |value| from the rounded published figures, so it can differ from NIST's own value in the last digit (e.g. 1.5e-10 vs 1.6e-10 for the fine-structure constant). Dimensionless constants have no unit.

Cite this dataset

AIDB. (2026). Fundamental physical constants (CODATA) [Data set]. NIST — CODATA Internationally Recommended Values of the Fundamental Physical Constants (complete listing). https://aidb.si/d/physical-constants

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