Instant · Precise · Universal
32 units available
6 categories total
To convert to meters: multiply by 2.8179403262 × 10⁻¹⁵.
re = e²/(4πε₀mec²) ≈ 2.8179 × 10⁻¹⁵ m, where e is electron charge and me is electron mass.
For example, 1 Electron Radius (Classical) (re) = 4.418124e-22 Earth's Equatorial Radius (R⊕ (eq)).
| Electron Radius (Classical) (re) | Earth's Equatorial Radius (R⊕ (eq)) |
|---|---|
| 0.1 | 4.418124e-23 |
| 0.5 | 2.209062e-22 |
| 1 | 4.418124e-22 |
| 2 | 8.836249e-22 |
| 5 | 2.209062e-21 |
| 10 | 4.418124e-21 |
| 25 | 1.104531e-20 |
| 50 | 2.209062e-20 |
| 100 | 4.418124e-20 |
| 500 | 2.209062e-19 |
| 1000 | 4.418124e-19 |
The classical electron radius is a theoretical length scale derived from the electron's charge and mass, approximately 2.818 × 10⁻¹⁵ meters.
re = e²/(4πε₀mec²) ≈ 2.8179 × 10⁻¹⁵ m, where e is electron charge and me is electron mass.
To convert to meters: multiply by 2.8179403262 × 10⁻¹⁵.
Used in calculating X-ray and gamma-ray scattering probabilities off electrons (Thomson and Compton scattering).
Despite its name, the electron is a point particle in quantum theory — the 'classical radius' is a theoretical construct, not the electron's actual size.
Assuming this is the actual physical size of the electron — quantum mechanics shows the electron has no measurable size.
Think of it as the scale at which classical electromagnetic self-energy equals the electron's mass-energy.
The Earth's equatorial radius is the distance from Earth's center to the equator, approximately 6,378.137 km.
R⊕(eq) = 6,378,137 m = 6,378.137 km. Earth's oblateness = (R_eq − R_pol)/R_eq ≈ 1/298.257.
To convert Earth radii to meters: multiply by 6,378,137.
GPS calculations, satellite orbit determination, map projections, and geophysical modeling.
Earth is not a perfect sphere — the equatorial radius is about 21 km (0.3%) larger than the polar radius due to rotational flattening.
Using the equatorial radius as if Earth were a sphere — for precision, you must account for the oblate spheroid shape.
Earth's equatorial radius (6,378 km) vs. polar radius (6,357 km) shows the planet bulges at the equator due to spinning.



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