Field strength measures the intensity of an electromagnetic field at a specific point. Electric field strength is measured in volts per meter (V/m), while magnetic field strength uses amperes per meter (A/m) or gauss/tesla.
Field strength decreases with distance from the source and is the primary metric used for assessing EMF exposure levels.
Field strength is the general term for how intense an electromagnetic field is at any given location. It’s what EMF meters measure, and it’s the metric that safety standards and exposure guidelines are based on.
For low-frequency EMF (from electrical sources), we measure two separate field strengths: electric field strength in volts per meter (V/m) and magnetic field strength in milligauss (mG) or microtesla (μT). These exist independently—you can have a strong electric field with a weak magnetic field, or vice versa.
For higher-frequency RF, the electric and magnetic components travel together as waves, so we often use power density instead. But field strength measurements (V/m for electric, A/m for magnetic) remain valid and are sometimes preferred in near-field conditions close to antennas.
The key practical point about field strength: it decreases with distance. For point sources, field strength often follows the inverse square law—double your distance, and the field drops to one-quarter strength. This is why distance is your most powerful tool for reducing EMF exposure.
Field strength also varies with the source’s power and design. A 100-watt light bulb creates a different field than a 1000-watt microwave oven. An unshielded cable creates different fields than a properly shielded one.
When using an EMF meter, you’re measuring field strength at your exact location. Walking toward or away from a source shows how dramatically readings change with position. This spatial variation is what makes EMF assessment a hands-on process—general statements about device emissions don’t tell you what you’re actually exposed to in your specific environment.
