Field Intensity Calculation

Below is a calculation tool to help determining the actual field intensity or power density (in V/M) at a given distance with a known antenna gain.
This calculation tool will assist:
  • The calculation of field intensity levels required by certain immunity standards.
  • Calculating the required power amplifier and antenna combinations for new testing requirements.
  • For safety (radiation hazard) or electromagnetic interference (EMI) effects.


Power: Watts
Antenna Gain:
Distance: Meters

Conversions are based on free space conditions (impedance of 377 ohm)


Field Strength Formula with Antenna Gain dBi

This calculation tool to help determining the required power to produce a desired field intensity using antenna gain and separation distance.

Desired V/M:
Antenna Gain:
Distance: Meters

Transmit Power Formula with Antenna Gain dBi

Field Intensity Calculation Microsoft Excel

Further Reading:

View our other RF Conversion formula sheets:
Useful formulas for RF related conversions
Magnetic field conversions
dBm to Volts to Watts conversion
VSWR Calculations

Product Showcase

Double Ridge Guide Horn Antenna

Double Ridge Guide Horn Antenna
  • 170 MHz to 3 GHz
  • Precision machined, Rugged Construction
  • High Power Input Capability

High gain, low VSWR, input handling capability up to 800 watts CW, and rugged design make this horn antenna excellent for both immunity and emissions testing.


Contact Details

A.H. Systems, inc.
9710 Cozycroft Ave.
Chatsworth, CA 91311

P: (818) 998-0223

F: (818) 998-6892

E: Email

Additional Resource

Antenna Beamwidth Coverage Calculations

Field Intensity Calculation

This tool will calculate the maximum coverage that the antenna will cover from a specified distance and antenna's half-power beamwidth. [more...]