Convert Volts/Meter to Volts/Mil

The Formula

Every unit here is defined by a fixed multiplier relative to the volt per meter. To convert a value from one unit to another:

result = value × (factor of "From" unit ÷ factor of "To" unit)

For Volt/Meter → Volt/Mil: multiply by 2.54E-05. For example, 1 V/m × 2.54E-05 = 2.54E-05 V/mil.

Two Ways to Define the Same Quantity

Electric field strength can be arrived at from two different directions that land on the exact same unit. The first is via electric potential: a field strength in volts per meter is simply how quickly potential changes as you move through space, so a 12-volt potential difference spread evenly across 1 meter is a 12 V/m field. The second is via force: the Lorentz force law, F = qE, defines the field E directly as the force it exerts on a charge divided by that charge's size, giving the equivalent unit newton per coulomb (N/C). Both routes describe the identical physical quantity, which is why volt/meter and newton/coulomb carry a conversion factor of exactly 1 on this page — physics textbooks introduce the force-based N/C definition first, then show the potential-based V/m form once students have covered electric potential.

Why Volt/Mil Matters in the Insulation Industry

A "mil" is one-thousandth of an inch, and volt/mil became the standard unit for dielectric strength in North American wire and cable manufacturing because insulation and coating thicknesses are conventionally specified in mils. Rating a material's breakdown strength directly in volts per mil lets an engineer compare it straight against a coating's thickness spec without converting units first — a wire insulation rated at 500 V/mil, for instance, can withstand about 500 volts for every mil (0.001 inch) of coating thickness before the material breaks down electrically. Because it is numerically equal to kilovolt/inch (both describe 1,000 volts across an inch of material, just grouped differently), the two units are often used interchangeably in engineering specifications.

Example

An electric field strength of 1 V/m equals 2.54E-05 V/mil. For scale, the electric field near the Earth's surface on a fair-weather day is roughly 100-150 volts per meter, the field inside a typical parallel-plate capacitor can reach several kilovolts per centimeter, and dry air begins to electrically break down (arc) at around 3 million volts per meter (3 kV/mm).

Frequently Asked Questions