Science, Tech, Math › Science Table of Physical Constants Commonly Used Constants Share Flipboard Email Print It's good to know the speed of light, one of the physical constants, since it is used in many calculations. Nick Koudis/Getty Images Science Chemistry Periodic Table Basics Chemical Laws Molecules Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Todd Helmenstine Todd Helmenstine is a science writer and illustrator who has taught physics and math at the college level. He holds bachelor's degrees in both physics and mathematics. our editorial process Todd Helmenstine Updated November 04, 2019 Need a value for a fundamental physical constant? Typically, these values are learned only in the short term as you are introduced to them and forgotten as soon as the test or task is finished. When they are needed again, constant searching through the textbook is one way to find the information again. A better way would be to use this handy reference table. Commonly Used Physical Constants Constant Symbol Value acceleration due to gravity g 9.8 m s-2 atomic mass unit amu, mu or u 1.66 x10-27 kg Avogadro's Number N 6.022 x 1023 mol-1 Bohr radius a0 0.529 x 10-10 m Boltzmann constant k 1.38 x 10-23 J K-1 electron charge to mass ratio -e/me -1.7588 x 1011 C kg-1 electron classical radius re 2.818 x 10-15 m electron mass energy (J) mec2 8.187 x 10-14 J electron mass energy (MeV) mec2 0.511 MeV electron rest mass me 9.109 x 10-31 kg Faraday constant F 9.649 x 104 C mol-1 fine-structure constant α 7.297 x 10-3 gas constant R 8.314 J mol-1 K-1 gravitational constant G 6.67 x 10-11 Nm2kg-2 neutron mass energy (J) mnc2 1.505 x 10-10 J neutron mass energy (MeV) mnc2 939.565 MeV neutron rest mass mn 1.675 x 10-27 kg neutron-electron mass ratio mn/me 1838.68 neutron-proton mass ratio mn/mp 1.0014 permeability of a vacuum μ0 4π x 10-7 N A-2 permittivity of a vacuum ε0 8.854 x 10-12 F m-1 Planck constant h 6.626 x 10-34 J s proton mass energy (J) mpc2 1.503 x 10-10 J proton mass energy (MeV) mpc2 938.272 MeV proton rest mass mp 1.6726 x 10-27 kg proton-electron mass ratio mp/me 1836.15 Rydberg constant r∞ 1.0974 x 107 m-1 speed of light in vacuum C 2.9979 x 108 m/s Physical Constants, Prefixes, and Conversion Factors List of Important Physical Constants Learn 3 Ways to Calculate Atomic Mass How to Help Students Take Notes What Is Avogadro's Number? Find the Ka or Equilibrium Constant Values of Weak Acids Specific Volume: What It Means And How to Calculate It Look Up Element Facts on the Clickable Periodic Table How to Prepare a Sodium Hydroxide Solution What Was Einstein Talking About With His Theory of Relativity? Why Instruction Methods Should Be Tailored to Each Student Text Features to Navigate Non-Fiction - Contents, Glossary and Index Creating a Positive Classroom Climate with Icebreakers Learn More About Wechsler Intelligence Tests Periodic Table of Atomic Masses Where Do I Find A Color Periodic Table of the Elements?