Safety Advice for Electromagnetic Fields


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Conversion Formulas

Jump to: Powerline | Microwave: V/m | dBm | W/m2          
See also: Inverse Square Law | Standards | Effects By Power

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

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