List of dimensionless quantities
This is a list of well-known dimensionless quantities illustrating their variety of forms and applications. The table does not include pure numbers, dimensionless ratios, or dimensionless physical constants; these topics are discussed in the article.
| Name | Standard symbol | Definition | Field of application |
| Abbe number | V | optics | |
| Activity coefficient | chemistry | ||
| Albedo | climatology, astronomy | ||
| Archimedes number | Ar | fluid mechanics | |
| Arrhenius number | chemistry | ||
| Atomic weight | M | chemistry | |
| Atwood number | A | fluid mechanics | |
| Bagnold number | Ba | fluid mechanics, geology | |
| Basic reproduction number | number of infections caused on average by an infectious individual over entire infectious period | epidemiology | |
| Bejan number | Be | fluid mechanics | |
| Bejan number | Be | thermodynamics | |
| Bingham number | Bm | fluid mechanics, rheology | |
| Biot number | Bi | heat transfer | |
| Blake number | Bl or B | geology, fluid mechanics, porous media | |
| Bodenstein number | Bo or Bd | chemistry | |
| Bond number | Bo | geology, fluid mechanics, porous media | |
| Brinkman number | Br | heat transfer, fluid mechanics | |
| Brownell–Katz number | NBK | fluid mechanics | |
| Capillary number | Ca | porous media, fluid mechanics | |
| Chandrasekhar number | Q | magnetohydrodynamics | |
| Colburn J factors | JM, JH, JD | turbulence; heat, mass, and momentum transfer | |
| Coefficient of kinetic friction | mechanics | ||
| Coefficient of static friction | mechanics | ||
| Coefficient of determination | statistics | ||
| Coefficient of variation | statistics | ||
| Cohesion number | Coh | Chemical engineering, material science, mechanics | |
| Correlation | ρ or r | statistics | |
| Cost of transport | COT | energy efficiency, economics | |
| Courant–Friedrich–Levy number | C or ? | mathematics | |
| Damkohler number | Da | chemistry | |
| Damping ratio | mechanics | ||
| Darcy friction factor | Cf or fD | fluid mechanics | |
| Darcy number | Da | porous media | |
| Dean number | D | turbulent flow | |
| Deborah number | De | rheology | |
| Decibel | dB | acoustics, electronics, control theory | |
| Drag coefficient | cd | aeronautics, fluid dynamics | |
| Dukhin number | Du | colloid science | |
| Eckert number | Ec | convective heat transfer | |
| Ekman number | Ek | geophysics | |
| Elasticity | E | economics | |
| Eötvös number | Eo | fluid mechanics | |
| Ericksen number | Er | fluid dynamics | |
| Euler number | Eu | hydrodynamics | |
| Euler's number | e | mathematics | |
| Excess temperature coefficient | heat transfer, fluid dynamics | ||
| Fanning friction factor | f | fluid mechanics | |
| Feigenbaum constants | , | chaos theory | |
| Fine-structure constant | quantum electrodynamics | ||
| f-number | f | optics, photography | |
| Föppl–von Kármán number | virology, solid mechanics | ||
| Fourier number | Fo | heat transfer, mass transfer | |
| Fresnel number | F | optics | |
| Froude number | Fr | fluid mechanics | |
| Gain | – | electronics | |
| Gain ratio | – | bicycling | |
| Galilei number | Ga | fluid mechanics | |
| Golden ratio | mathematics, aesthetics | ||
| Görtler number | G | fluid dynamics | |
| Graetz number | Gz | heat transfer, fluid mechanics | |
| Grashof number | Gr | heat transfer, natural convection | |
| Hatta number | Ha | chemical engineering | |
| Hagen number | Hg | heat transfer | |
| Havnes parameter | In Dusty plasma physics, ratio of the total charge carried by the dust particles to the charge carried by the ions , with the number density of particles | ||
| Helmholtz number | The most important parameter in duct acoustics. If is the dimensional frequency, then is the corresponding free field wavenumber and is the corresponding dimensionless frequency | ||
| Hydraulic gradient | i | fluid mechanics, groundwater flow | |
| Iribarren number | Ir | wave mechanics | |
| Jakob number | Ja | chemistry | |
| Karlovitz number | Ka | turbulent combustion | |
| Keulegan–Carpenter number | KC | fluid dynamics | |
| Knudsen number | Kn | gas dynamics | |
| Kt/V | Kt/V | medicine | |
| Kutateladze number | Ku | fluid mechanics | |
| Laplace number | La | fluid dynamics | |
| Lewis number | Le | heat and mass transfer | |
| Lift coefficient | CL | aerodynamics | |
| Lockhart–Martinelli parameter | two-phase flow | ||
| Love numbers | h, k, l | geophysics | |
| Lundquist number | S | plasma physics | |
| Mach number | M or Ma | gas dynamics | |
| Magnetic Reynolds number | Rm | magnetohydrodynamics | |
| Manning roughness coefficient | n | open channel flow | |
| Marangoni number | Mg | fluid mechanics | |
| Markstein number | fluid dynamics, combustion | ||
| Morton number | Mo | fluid dynamics | |
| Nusselt number | Nu | heat transfer | |
| Ohnesorge number | Oh | fluid dynamics | |
| Péclet number | Pe | heat transfer | |
| Peel number | NP | coating | |
| Perveance | K | charged particle transport | |
| pH | chemistry | ||
| Pi | mathematics | ||
| Pierce parameter | Traveling wave tube | ||
| Pixel | px | digital imaging | |
| Beta | Plasma and Fusion power. Ratio of plasma thermal pressure to magnetic pressure, controlling the level of turbulence in a magnetised plasma. | ||
| Poisson's ratio | elasticity | ||
| Porosity | geology, porous media | ||
| Power factor | pf | electrical | |
| Power number | Np | electronics | |
| Prandtl number | Pr | heat transfer | |
| Prater number | β | reaction engineering | |
| Pressure coefficient | CP | aerodynamics, hydrodynamics | |
| Q factor | Q | physics, engineering | |
| Radian measure | rad | mathematics | |
| Rayleigh number | Ra | heat transfer | |
| Refractive index | n | electromagnetism, optics | |
| Relative density | RD | hydrometers, material comparisons | |
| Relative permeability | magnetostatics | ||
| Relative permittivity | electrostatics | ||
| Reynolds number | Re | fluid mechanics | |
| Richardson number | Ri | fluid dynamics | |
| Rockwell scale | – | mechanical hardness | |
| Rolling resistance coefficient | Crr | vehicle dynamics | |
| Roshko number | Ro | fluid dynamics | |
| Rossby number | Ro | geophysics | |
| Rouse number | P or Z | sediment transport | |
| Schmidt number | Sc | mass transfer | |
| Shape factor | H | boundary layer flow | |
| Sherwood number | Sh | mass transfer | |
| Shields parameter | or | sediment transport | |
| Sommerfeld number | S | hydrodynamic lubrication | |
| Specific gravity | SG | ||
| Stanton number | St | heat transfer and fluid dynamics | |
| Stefan number | Ste | phase change, thermodynamics | |
| Stokes number | Stk or Sk | particles suspensions | |
| Strain | materials science, elasticity | ||
| Strouhal number | St or Sr | fluid dynamics | |
| Stuart number | N | magnetohydrodynamics | |
| Taylor number | Ta | fluid dynamics | |
| Transmittance | T | optics, spectroscopy | |
| Ursell number | U | wave mechanics | |
| Vadasz number | Va | porous media | |
| van 't Hoff factor | i | quantitative analysis | |
| Wallis parameter | j* | multiphase flows | |
| Wagner number | Wa | electrochemistry | |
| Weaver flame speed number | Wea | combustion | |
| Weber number | We | multiphase flow | |
| Weissenberg number | Wi | viscoelastic flows | |
| Womersley number | biofluid mechanics | ||
| Zel'dovich number | fluid dynamics, Combustion |