Name Symbol Value Absolute Zero -273.16 ĄC Acceleration of Free Fall g 9.80665 ms-2 Acre 4046.86 m2 Air, Density of (at stp) 0.7734 m3 kg-1 1.2929 kg m-3 ngstršm  10e-10 m Astronomical Unit AU 1.4959787 E+11 m Atomic Mass Constant m_u, u 1.660 540 2 E-27 kg 931.494 32 MeV Avogadro Constant L 6.022 136 7 E+23 mol-1 Base of Natural Logarithms e 2.718 281 828 Board Foot (Timber 2.359 ?10-3 m3 Bohr Magneton mu_B 9.274 015 4 E-24 J T-1 5.788 382 63 E-5 eV T-1 1.399 624 18 E+10 Hz T-1 46.686 437 m-1 T-1 0.671 709 9 K T-1 Bohr Radius a_0 5.291 772 49 x10-11 m Boltzmann Constant k 1.380 658 x10-23 J k-1 8.617 385 x10-5 eV K-1 2.083 674 x1010 Hz K-1 69.503 87 m-1 K-1 Chain 20.1168 m Classical Electron Radius r_e 2.817 940 92 x10-15 m Compton Wavelength lamda_c 2.426 310 58 x10-12 m 3.861 593 23 x10-13 m Cord (Timber) 3.624 m3 Critical Temperature of Air -190 ĄC 183 K Curie Ci 3.7 E+10 Bq Density of Air at stp 1.2929 kg m-3 Dirac's Constant h_bar 1.0545887 x10-34 Js Dram (Avoirdupois) 1.771 g Dry Pint, US 5.506 ?10-4 m3 e 2.718 281 828 Earth's Average Density 5.517 ?103 kg m-3 Earth's Average Radius R 6.37 ?106 m Earth's Mass M 5.972 ?1024 kg Electrical Power UK 230V ac, 50Hz Electrical Power USA 115V ac, 60Hz Elect-alpha-Part Mass Ratio m_e/m_alpha 1.370 933 54 x10-4 Electron Charge e 1.602 177 33 x10-19 C Electron-Deuteron Mass Ratio m_e/m_d 2.724 437 07 x10-4 Electron g-Factor g_e 2.002 319 304 386 Electron Magnetic Moment mu_e 928.477 01 x10-28 m2 mu_e/mu_ B 1.001 159 652 193 mu_e/mu_ N 1.838 282 000 Electron Magn Moment Anomaly a_e 1.159 652 193 x10-3 Electron Mass m_e 9.109 389 7 x10-31 kg 5.485 799 03 x10-4 u 0.510 999 06 MeV Electron Molar Mass M(e), Me 5.485 799 03 x10-7 kg mol-1 Elect-Muon Magn Moment Ratio mu_e/mu_mu 206.766 967 Electron-Muon Mass Ratio m_e/m_mu 4.836 332 18 x10-3 Elect-Proton Magn Mom Ratio mu_e/mu_p 658.210 688 1 Electron-Proton Mass Ratio m_e/m_p 5.446 170 13 x10-4 Electron Specific Charge -e/m_e -1.758 819 62 x1011 C kg-1 Electronvolt eV 1.6021892 x10-19 J Elementary Charge e 1.602 177 33 x10-19 C e/h 2.417 988 36 x1014 A J-1 emf of Daniell Cell 1.08 V emf of LechlanchŽ Cell 1.46 V emf of Nife Cell 1.40V emf of Weston Cell 1.0186 V Faraday Constant F 96 485.309 C mol-1 Fathom 1.8288 m Feigenbaum's Constant delta 4.669 210 609 102 990 Fine Structure Constant alpha 7.29735308 x10-3 First Radiation Constant c_1 3.741 774 9 x10-16 W m2 Fluid Ounce, UK 2.841 ?10-5 m3 Fluid Ounce, US 2.957 ?10-5 m3 Foot ft, ' 0.3048 m Foot (Timber), Board 2.359 ?10-3 m3 Gallon, UK 1.201 US gallon 4.546 ?10-3 m3 Gallon, US 0.833 UK gallon 3.785 ?10-3 m3 Grain 0.064 79 g Gravitational Constant G 6.67 ? 10-11 N m2 kg-2 Half-life of Carbon-14 T 5570 years Half-life of Free Neutron T 650 s Hartree Energy E_h 4.359 748 2 x10-18 J 27.211 396 1 eV Hectare ha 104 m2 Earth's Magnetic (Horz)Field B0 1.8 ?10-5 T Hundredweight (UK) cwt 5.08 ? 104 g Hundredweight, Short (US) short cwt 4.535 ? 104 g Hydrogen Rydberg Number RH 1.096 775 8 ?107 m-1 Imperial Pint 5.682 ?10-4 m3 Inch in, " 0.254 m International Nautical Mile 1852 m Inverse Fine Structure Const alpha 7.297 353 08 x10-3 Josephson Frequ Volt Quotient 2e/h 4.835 976 7 x1014 Hz V-1 Light Year 9.5 ?1015 m Linear Expansivity of Copper alpha 1.7 ?10-5 K-1 Linear Expansivity of Steel alpha 1.2 ?10-5 K-1 Liquid Pint, US 4.731 ?10-4 m3 Litre 10-3 m3 Loschmidt Constant n0 2.686 763 x1025 m-3 Loschmidt Constant (T = 273.15 K, p = 100 kPa) See Molar Volume V_m 0.022 711 08 m3 mol-1 Magnetic Flux Quantum Phi_0 2.067 834 61 x10-15 Wb Mile 1609.34 m Mile, International Nautical 1852 m Mile, UK Nautical 1853.18 m Million Electron Volts MeV 1.6 ?10-13 J Molar Gas Constant R 8.314 510 J mol-1 K-1 Molar Planck Constant N_A_h 3.990 313 23 x10-10 J s mol-1 N_A_h_c 0.119 626 58 J m mol-1 Molar Volume (Ideal Gas, T = 273.15 K, p = 101.325 kPa) Vm 0.022 414 10 m3 mol-1 Moon's Grav Acceleration 1.619 m s-2 Moon's Mean Density 3.33 ?103 kg m-3 Moon's Mean Distance to Earth 3.844 ?108 m Moon's Mean Mass 7.33 ?1022 kg Moon's Mean Radius 1.738 ?106 m Muon-Electron Mass Ratio M_mu/m_e 206.768 262 Muon g-Factor g_mu 2.002 331 846 Muon Magnetic Ano maly a_mu 1.165 923 0 x10-3 Muon Magnetic Moment Mu_mu 4.490 451 4 x10-26 J T-1 Mu_mu/mu_B 4.841 970 97 x10-3 Mu_mu/mu_N 8.890 596 1 Muon Mass m_mu 1.883 532 7 x10-28 kg 0.113 428 913 u 105.658 389 MeV Muon Molar Mass M(mu), M_mu 1.134 289 13 x10-4 kg mol-1 Muon-Proton Magn Moment Ratio M_mu/mu_P 3.183 345 47 Nautical Mile, International 1852 m Nautical Mile, UK 1853.18 m Newtonian Constant of Gravi G 6.672 59 ?10-11 m3 kg-1 s-2 Nuclear Magneton mu_N 5.050 786 6 ?10-27 J T-1 3.152 451 66 ?10-8 eV T-1 7.622 591 4 MHz T-1 2.542 622 81 ?10-2 m-1 T-1 3.658 246 ?10-4 K T-1 Ounce, Avoirdupois oz 28.349 g Ounce, Troy/Apothecaries' 31.103 g Ounce, UK Fluid 2.841 ?10-5 m3 Ounce, US Fluid 2.957 ?10-5 m3 Permeability of Free Space mu_0 4 ?10-7 N A-2 12.566 370 614 ? 10-7 N A-2 Permittivity of Free Space epsilon_0 8.854 187 817 ?10-12 F m-1 Pint, US Dry 5.506 ?10-4 m3 Pint, Imperial 5.682 ?10-4 m3 Pint, US Liquid 4.731 ?10-4 m3 Planck Constants h 6.626 075 5 ?10-34 J s 4.135 669 2 ?10-15 eV s Planck Constant (h / 2π) h 1.054 572 66 ?10-34 J s 6.582 122 0 ?10-16 eV s Planck Mass m_P 2.176 71 ?10-8 kg Planck Length l_P 1.616 05 ?10-35 m Planck Time t_P 5.390 56 ?10-44 s Pound lb 0.453 592 37 kg Quantized Hall Conductance e^2 / h 3.874 046 14 ? 10-5 S Quantized Hall Resistance R_H 25 812.805 6 Ω Quantum of Circulation h / 2*m_e 3.636 948 07 ?10-4 m2 s-1 h / m_e 7.273 896 14 ?10-4 m2 s-1 Refractive Index of Glass n_g 1.50 Refractive Index of Paraffin n_p 1.42 Refractive Index of Water n_w 1.33 Rydberg Constant R_infinty 10 973 731.534 m-1 3.289 841 949 9 ?1015 Hz 2.179 874 1 ?10-18 J 13.605 698 1 eV Rydberg Number, Hydrogen R_H 1.096 775 8 ?107 m-1 Second Radiation Constant c_2 0.014 387 69 m K Short Hundredweight short cwt 4.535 ? 104 g Short Ton 2000 lb 9.071 ? 105 g Slug 1.459 ? 104 g Solar Constant 1400 W m-2 Specific Heat Capac Copper c_c 385 J kg-1 K-1 Specific Heat Cap Water c_w 4200 J kg-1 K-1 Spec Latent Heat Fus Water L 3.34 ?105 J kg-1 SpecLatent Heat Vapor Water L 2.26 ?106 J kg-1 Speed of Light in a Vacuum c 299 792 458 m s-1 Speed Sound in Air STP v 340 m s-1 Stefan-Boltzmann Constant sigma 5.670 51 ?10-8 W m-2 K-4 Sun's Energy Production 3.90 ?1026 W Sun's Mass 1.99 ?1030 kg Sun's Mean Distanceto Earth 1.495 ?1011 m Sun's Mean Radius 6.960 ?108 m Thermal Conductivity Copper k 385 W m-1 K-1 Thermal Conductivity Glass k 1.0 W m-1 K-1 Thomson Cross Section sigma_e 0.665 246 16 ?10-28 m2 Tonne 106 g Ton, Short 2000 lb 9.071 ? 106 g Ton, UK 1.016 ? 106 g UK Fluid Ounce 2.841 ?10-5 m3 UK Gallon 1.201 US gallon 4.546 ?10-3 m3 UK Nautical Mile 1853.18 m Universal Constant Gravi G 6.67 ? 10-11 N m2 kg-2 US Dry Pint 5.506 ?10-4 m3 US Fluid Ounce 2.957 ?10-5 m3 US Gallon 0.833 UK gallon 3.785 ?10-3 m3 US Liquid Pint 4.731 ?10-4 m3 Velocity Sound Air STP v 340 m s-1 Viscosity of Air at 20 ĄC eta_0 1.8 ?10-5 N s m-2 Viscosity of Water at 20 ĄC eta_w 1.002 ?10-3 N s m-2 Wien Displacement Law Cons b 2.897 756 ?10-3 m K Yard yd 0.9144 m Young Modulus for Copper E 1.3 ?1011 Pa Young Modulus for Steel E 2.1 ?1011 Pa SI Base Units Quantity Name Symbol Length metre m Mass kilogram kg Time second s Electric Current ampere A Thermodc Temp kelvin K Amount Substance mole mol Luminous Intensi candela cd Frequency hertz Hz s-1 Force newton N m kg s-2 Pressure / Stress pascal Pa N/m2 m-1 kg s-2 Quantity of Heat joule J N m m2 kg s-2 PowerRadiant Flux watt W J/s m2 kg s-3 Electric Charge coulomb C s A Electric Potential volt V W/A m2 kg s-3 A-1 Capacitance farad F C/V m-2 kg-1 s4 A3 Elec Resistance ohm omaga V/A m2 kg s-2 A-1 Elec Conductance siemens S A/V m-2 kg-1 s3 A2 Magnetic Flux weber Wb V s m2 kg s-2 A-1 Mag Flux Density tesla T Wb/m2 kg s-2 A-1 Inductance henry H Wb/A M2 kg s-2 A-2 Celsius Temp degree celsius ĄC K Luminous Flux lumen lm cd sr Illuminance lux lx lm/m2 m-2 cd sr ActivRadionuclide bequerel Bq s-1 Absorbed Dose Index gray Gy J/kg m2 s-2 AbsorbDoseEnergy Dose Equi Index sievert Sv J/kg m2 s-2 Dynamic Viscosity Pa s m-1 kg s-1 Moment of Force N m M2 kg s-2 Surface Tension N/m kg s-2 Heat Flux Density Irradiance W/m2 kg s-3 Heat Capacity / Entropy J/K M2 kg s-2 K-1 Spec Heat Capac Spec Entropy J/(kg K) m2 s-2 K-1 Specific Energy J/kg M2 s-2 Thermal Conductivity W/(m K) m kg s-3 K-1 Energy Density J/m3 m-1 kg s-2 Electric Field Strength V/m m kg s-3 A-1 Electric Charge Density C/m3 m-3 s A Electric Flux Density C/m2 m-2 s A Permittivity F/m m-3 kg-1 s4 A2 Permeability H/m m kg s-2 A-2 Molar Energy J/mol m2 kg s-2 mol-1 MolarEntropy/MolarHeatCapac J/(mol K) m2 kg s-2 K-1 mol-1 Exposure (x/gama rays) C/kg kg-1 s A AbsorbDoseRate (gray/sec) Gy/s M2 s-3 Plane Angle radian rad m m-1 = 1 Solid Angle steradian sr m2 m-2 = 1 Symbol Angular Velocity rad/s Angular Acceler rad/s2 Radiant Intensity W/sr Radiance W/(m2 sr)