Safety Advice for Electromagnetic Fields (PDF)
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# Conversion Formulas

The following formulas are useful for estimating the exposure from power line technologies and wireless technologies.

# Conversion Formulas for Powerline Magnetic Fields

## Formula for Conversion from milligauss (mG) to microTesla (μT)

1 milligauss = 0.1 microtesla

1 microtesla = 10 milligauss

# Conversion Formulas for Wireless (Radio/Microwave) Emissions

## Conversion from Power Density units: mW/cm2 to W/m2 and μW/cm2 to mW/m2

1 mW/cm2 = 10,000 mW/m2 = 10W/m2

1 μW/cm2 = 10,000 μW/m2=10mW/m2

## Formula for Conversion from Power Density (W/m2) to Electric Field Intensity (V/m)

V/m = (W/m2 x 377)1/2

Example: 1 mW/m2 = (0.001 * 377)1/2 V/m = 0.6 V/m

## Formula for Conversion from Electric Field Intensity (V/m) to Power Density (W/m2)

W/m2 = (V/m)2 / 377

Example: 0.6 V/m = (0.6)(0.6)/377 W/m2 = 0.001 W/m2 = 1 mW/m2

## Formula for Conversion from dbM to Transmit Power (mW)

dBm = 10 * log10(mW)

Example: 31 mW = 10 * log1031 = 15 dBm

## Formula for Conversion from Transmit Power (mW) to dbM

mW = 10^(dBm/10)

Example: 15 dBm = 10^1.5 = 31 mW

## Formula for Conversion from Transmit Power (mW) to Power Density

Note that this formula provides the power density assuming uniform distribution of power in all directions. Since the distribution of a cell tower may include side lobes, keep in mind that some directions can have higher power density than others.

Power Density = P/4Πr2

where P is the Transmit Power, r is the distance, and 4Πr2 is the surface area of a sphere.

Example: 31 mW at r=1m distance translates to 31/4*Π*(1)2 = ~2.5 mW/m2