In physics, Stoney scale is the fundamental scale, named after the Irish physicist George Johnstone Stoney, who first proposed the ‘’elementary electric charge’’ in 1881.  It defines that fine structure constant is equal to gravitational coupling constant (and to electric coupling constant) of Stoney scale:
There is the dimensionless magnetic coupling constant that could be named as the Stoney scale force constant since it defines the force interactions (electric, gravitational, etc.) in the Stoney scale.
Contemporary physics has settled on the Planck scale as the most suitable scale for the unified field theory. The Planck scale was however anticipated by George Stoney. 
James G. O’Hara  pointed out in 1974 that Stoney’s derived estimate of the unit of charge,
10-20 Ampere (later called the Coulomb), was 1⁄16 of the correct value of the charge of the electron. Stoney used the quantity 1018 for the number of molecules presented in one cubic millimeter of gas at standard temperature and pressure. Using Avogadro constant 6.0221×1023
, and the volume of a mole (at standard conditions) of 22.711×106
mm3, we derive, instead of 1018, the estimate 2.652×1016
. So, if Stoney could use the true number of molecules his estimate of the unit of charge was about 1⁄2 of the correct value of the charge.
For a long time the Stoney scale was in the shadow of the Planck scale (something like a "deviation" of it). However, after intensive investigation of gravitation by using the Maxwell-like gravitational equations during last decades, became clear that Stoney scale is independent scale of matter.
Fundamental units of vacuum
The set of primary vacuum constants is: the speed of light ; the electric constant ; the speed of gravity (usually equated to the speed of light); the gravitational constant .
The set of secondary vacuum constants is:
The vacuum permeability: ;
The electromagnetic impedance of free space:
The gravitoelectric gravitational constant:
The gravitomagnetic gravitational constant:
The gravitational characteristic impedance of free space:
Note that all Stoney and Planck units are derivatives from the vacuum constants, therefore the last are more fundamental that units of any scale.
If the above fundamental constants define naturally the following relationship between mass and elementary charge for the Stoney mass:
and these constants are the base units of the Stoney scale.
Primary Stoney units
Gravitational Stoney units
where is the Planck mass.
Stoney gravitational fine structure constant:
Stoney fictitious gravitational torsion mass:
- J s kg−1.
Stoney scale gravitational torsion coupling constant: 
Stoney gravitational impedance quantum:
- J s kg−2.
Electromagnetic Stoney units
Stoney electric fine structure constant:
Stoney fictitious magnetic charge:
Stoney scale magnetic coupling constant:
Stoney electrodynamic impedance quantum:
which appears as the von Klitzing constant.
Secondary Stoney scale units
All systems of measurement feature is base units: in the International System of Units (SI), for example, the base unit of length is the meter. In the system of Stoney units, the Stoney base unit of length is known simply as the ‘’Stoney length’’, the base unit of time is the ‘’Stoney time’’, and so on. These units are derived from the presented above primary Stoney units, and arranged in Table 1 so as to cancel out the unwanted dimensions, leaving only the dimension appropriate to each unit. (Like all systems of natural units, Stoney units are an instance of dimensional analysis.)
The keys which are used in the Tables below: L = length, T = time, M = mass, Q = electric charge, Θ = temperature.
Table 1: Secondary Stoney units
||SI equivalent 
|Stoney classical radius
|Stoney Schwarzschild radius
Derived Stoney scale units
In any system of measurement, units for many physical quantities can be derived from base units. Table 2 offers a sample of derived Stoney units, some of which in fact are seldom used.
As with the base units, their use is mostly confined to theoretical physics because most of them are too large or too small for empirical or practical use and there are large uncertainties in their values.
Table 2: Derived Stoney units
||Momentum (LMT −1)
|| kg m/s
||Energy (L2MT −2)
||Force (LMT −2)
||Power (L2MT −3)
|Stoney angular frequency
||Frequency (T −1)
|| rad s−1
||Pressure (L−1MT −2)
||Electric current (QT −1)
||Voltage (L2MT −2Q−1)
|Stoney electric impedance
||Resistance (L2MT −1Q−2)
|Stoney gravitational current
||Gravitational current (MT −1)
|| kg s−1
|Stoney gravitational potential
||Gravitational potential (L2T −2)
|| m2 s−2
|Stoney gravitational impedance
||Gravitational impedance (L2M −1T −1)
|| m2 kg−1 s−1
|Stoney electric capacitance per unit area
||Electric capacitance (L−4M−1T2Q2)
|| F m−2
|Stoney electric inductance per unit area
||Electric inductance (L2MQ−2)
|| H m−2
|Stoney gravitational capacitance per unit area
||Gravitational capacitance (L−4MT2 )
|| m−4 kg s2
|Stoney gravitational inductance per unit area
||Gravitational inductance (L2M−1)
|| m2 kg−1
|Stoney particle radius
|Stoney particle area
Stoney scale forces
Stoney scale static forces
Electric Stoney scale force:
Gravity Stoney scale force:
where is the gravitational fine structure constant.
Mixed (charge-mass interaction) Stoney force:
So, at the Stoney scale we have the equality of all static forces which describes interactions between charges and masses:
Stoney scale dynamic forces
Magnetic Stoney scale force:
where is the fictitious elementary magnetic charge,
is the magnetic coupling constant.
Gravitational torsion force:
where is the fictitious gravitational torsion mass,
is the gravitational torsion coupling constant for the gravitational torsion mass .
Mixed dynamic (magnetic - torsion interaction) force:
So, at the Stoney scale we have the equality of all dynamic forces which describes interactions between dynamic charges and masses:
- ↑ 1.0 1.1 Stoney G. On The Physical Units of Nature, Phil.Mag. 11, 381–391, 1881
- ↑ J.G. O’Hara (1993). George Johnstone Stoney and the Conceptual Discovery of the Electron, Occasional Papers in Science and Technology, Royal Dublin Society 8, 5–28.
Yakymakha O.L.(1989). High Temperature Quantum Galvanomagnetic Effects in the Two- Dimensional Inversion Layers of MOSFET's (In Russian). Kyiv: Vyscha Shkola. p.91. ISBN 5-11-002309-3. djvu
- ↑ Latest (2010) values of the constants