Energy Density of Fields Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Small changes can matter a lot in energy density of fields. Electromagnetic calculations are easiest to audit when voltage, current, field, charge, frequency, and geometry are kept in their correct roles. Use the calculator as a transparent first model, then decide whether your real system needs a more detailed treatment.

What this calculator does

Use this page to evaluate electromagnetic energy density from Electric field strength, Magnetic field (B). The result is most useful when the entered quantities describe one consistent physical setup and the displayed units stay attached to the number.

How to use it

Use measured, specified, or deliberately hypothetical values for Electric field strength, Magnetic field (B). Keep the quantity definitions and unit prefixes exactly as labeled; a correct number in the wrong physical quantity or prefix will still produce a misleading result.

How the calculation works

Total electromagnetic energy density is u = ½ε0E² + B²/(2μ0). The page reports electric and magnetic contributions separately as well as their sum.

Example

With the default setup (Electric field strength = 1000 V/m; Magnetic field (B) = 0 T), the page reports electromagnetic energy density of 0.000004 J/m³. Treat the example as a consistency check, not a universal design target; its meaning depends on the inputs and assumptions above.

How to interpret the result

Read the electromagnetic energy density with its sign, magnitude, phase, frequency, geometry, and unit as applicable. A field, reactance, power factor, loss, or flux value should be compared only with a quantity defined in the same way.

Limitations and notes

Real electrical and magnetic systems can add parasitics, finite geometry, temperature dependence, nonlinear materials, frequency-dependent losses, tolerances, and measurement uncertainty beyond the ideal relationship shown here. Pay particular attention to Electric field strength, Magnetic field (B) and their units. A mathematically correct result can still be incomplete when the real system includes effects not represented on the form.