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Scientific Unit Converter

Convert between SI, CGS / ESU, and atomic units for the quantities that matter in nanophotonics, quantum mechanics, and electromagnetism.

v1.0.0·Updated 2026-06-10
Model & Assumptions Stable
Model
Exact unit-conversion factors between SI, Gaussian CGS/ESU, and Hartree atomic units for 11 electromagnetic and mechanical quantities.
Assumptions
Conversion factors follow CODATA 2018 recommended values. CGS/ESU uses the Gaussian convention (unrationalized, ε0 = 1/4π).
Limitations
Conversions are exact within floating-point precision. Does not cover Heaviside–Lorentz or natural units.

Magnitude

Mechanical
Energy & waves
Electromagnetic

Fundamental Constants

SIESUAU
c3.00e83.00e10137
ℏ1.05e-341.05e-271
ε08.85e-127.96e-27.96e-2
q1.60e-194.80e-101
me9.11e-319.11e-281
a05.29e-115.29e-91
SI m
SI (nano) nm
SI (femto) fm
ESU / CGS cm
Atomic units a.u.