Energy Density of Electric and Magnetic Fields Calculator

Your details

Forward mode calculates energy density from E and B. Reverse modes solve for the field that produces a given energy density.
Choose vacuum to use the fundamental constants of free space. Choose custom to model a dielectric or magnetic material.
Peak or RMS electric field in volts per metre. Earth surface field is about 100-300 V/m; inside a capacitor it can reach MV/m.
V/m
Magnetic flux density in tesla. Earths surface field is about 25-65 µT; an MRI machine is 1.5-3 T.
T
If you enter a volume, the calculator also reports the total energy stored in that region (U = u × V). Leave blank or set to 0 to skip.
m³
Total energy densityModerate density
0.3979J/m³

Combined electric plus magnetic energy density: u = uE + uB

Electric energy density (uE)0J/m³
Magnetic energy density (uB)0.3979J/m³
Total energy stored0.0004J
Electric share0%
Magnetic share100%

Total energy density: 0.397892 J/m³

  • The magnetic field dominates, contributing 100.0% of the total energy density.
  • The 0.001 m³ region stores 3.979e-4 J of electromagnetic energy in total.
  • For a plane wave in vacuum the electric and magnetic energy densities are always exactly equal, and the total density is u = ε₀E² = B²/μ₀.
  • Energy density is an intensive quantity: it tells you how concentrated the energy is, not how much energy there is in total. You need the volume to get the total.

Next stepTo go further, enter the volume of your capacitor, inductor core, or antenna near-field region to calculate the total energy stored.

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