{
  "collection": "quantities",
  "name": "Quantities & units",
  "description": "The physical quantities used in EMF work, their units, exact conversion factors, and the formulas relating them.",
  "count": 7,
  "dataVersion": "2026.08.1",
  "lastVerified": "2026-08-12",
  "license": {
    "name": "CC BY 4.0",
    "url": "https://creativecommons.org/licenses/by/4.0/"
  },
  "records": [
    {
      "id": "quantities:magnetic-flux-density",
      "collection": "quantities",
      "slug": "magnetic-flux-density",
      "name": "Magnetic flux density",
      "summary": "The quantity an ELF gaussmeter reports, expressed in milligauss or microtesla, used to assess wiring, transformers and power lines. 1 µT = 10 mG.",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "B field",
          "magnetic field",
          "gauss",
          "tesla"
        ],
        "quantityId": "magnetic-flux-density",
        "symbol": "B",
        "siUnit": "T",
        "units": [
          {
            "symbol": "T",
            "name": "tesla",
            "toBase": 1
          },
          {
            "symbol": "mT",
            "name": "millitesla",
            "toBase": 0.001
          },
          {
            "symbol": "µT",
            "name": "microtesla",
            "toBase": 0.000001
          },
          {
            "symbol": "nT",
            "name": "nanotesla",
            "toBase": 1e-9
          },
          {
            "symbol": "G",
            "name": "gauss",
            "toBase": 0.0001
          },
          {
            "symbol": "mG",
            "name": "milligauss",
            "toBase": 1e-7
          }
        ],
        "measures": "Magnetic component of a low-frequency field. Passes through walls and almost all shielding materials, so mitigation is by distance or by fixing the current imbalance that creates it.",
        "conversions": [
          {
            "to": "magnetic-flux-density",
            "formula": "H (A/m) = B (µT) / 1.25663706",
            "note": "Magnetic field strength H relates to flux density B by the permeability of free space, µ₀ = 4π × 10⁻⁷ H/m. 1 A/m ≈ 1.2566 µT in air."
          }
        ],
        "related": [
          "limits:sbm-2024-magnetic-bands",
          "limits:icnirp-2010-public-magnetic-50-60"
        ]
      },
      "sources": [
        {
          "id": "nist-si",
          "title": "The International System of Units (SI), NIST Special Publication 330",
          "publisher": "National Institute of Standards and Technology",
          "url": "https://www.nist.gov/pml/special-publication-330",
          "kind": "government",
          "retrieved": "2026-08-12"
        },
        {
          "id": "sbm-2024",
          "title": "Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024)",
          "publisher": "Institut für Baubiologie + Nachhaltigkeit (IBN)",
          "url": "https://buildingbiology.com/site/downloads/SBM-2024_EVALUATION_GUIDELINES_EN.pdf",
          "year": 2024,
          "kind": "ngo",
          "retrieved": "2026-08-12"
        }
      ],
      "links": {
        "self": "https://emfbase.com/api/quantities/magnetic-flux-density",
        "html": "https://emfbase.com/quantities/magnetic-flux-density",
        "markdown": "https://emfbase.com/quantities/magnetic-flux-density.md",
        "collection": "https://emfbase.com/api/quantities"
      }
    },
    {
      "id": "quantities:electric-field-strength",
      "collection": "quantities",
      "slug": "electric-field-strength",
      "name": "Electric field strength",
      "summary": "Volts per metre, reported both for power-frequency electric fields near wiring and for radiofrequency fields near transmitters.",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "E field",
          "V/m",
          "volts per meter"
        ],
        "quantityId": "electric-field-strength",
        "symbol": "E",
        "siUnit": "V/m",
        "units": [
          {
            "symbol": "kV/m",
            "name": "kilovolt per metre",
            "toBase": 1000
          },
          {
            "symbol": "V/m",
            "name": "volt per metre",
            "toBase": 1
          },
          {
            "symbol": "mV/m",
            "name": "millivolt per metre",
            "toBase": 0.001
          },
          {
            "symbol": "µV/m",
            "name": "microvolt per metre",
            "toBase": 0.000001
          }
        ],
        "measures": "Electric component of the field. At power frequency it is easily blocked by grounded conductive surfaces; at radiofrequency it is one of two interchangeable ways to express far-field exposure.",
        "conversions": [
          {
            "to": "power-density",
            "formula": "S (W/m²) = E² / 377",
            "note": "Valid in the far field of an antenna, where the wave impedance equals the impedance of free space, 376.73 Ω. Not valid within a wavelength of the source."
          },
          {
            "to": "electric-field-strength",
            "formula": "dBµV/m = 20 · log₁₀(E in µV/m)",
            "note": "Logarithmic form used by spectrum analysers and EMC test equipment."
          }
        ]
      },
      "sources": [
        {
          "id": "nist-si",
          "title": "The International System of Units (SI), NIST Special Publication 330",
          "publisher": "National Institute of Standards and Technology",
          "url": "https://www.nist.gov/pml/special-publication-330",
          "kind": "government",
          "retrieved": "2026-08-12"
        },
        {
          "id": "itu-fs-relations",
          "title": "Free-space path loss and power density relations (ITU-R P.525)",
          "publisher": "International Telecommunication Union",
          "url": "https://www.itu.int/rec/R-REC-P.525/en",
          "kind": "standard",
          "retrieved": "2026-08-12"
        },
        {
          "id": "fcc-1310",
          "title": "47 CFR § 1.1310 — Radiofrequency radiation exposure limits",
          "publisher": "U.S. Government Publishing Office (eCFR)",
          "url": "https://www.ecfr.gov/current/title-47/section-1.1310",
          "kind": "regulation",
          "retrieved": "2026-08-12"
        }
      ],
      "links": {
        "self": "https://emfbase.com/api/quantities/electric-field-strength",
        "html": "https://emfbase.com/quantities/electric-field-strength",
        "markdown": "https://emfbase.com/quantities/electric-field-strength.md",
        "collection": "https://emfbase.com/api/quantities"
      }
    },
    {
      "id": "quantities:power-density",
      "collection": "quantities",
      "slug": "power-density",
      "name": "Power density",
      "summary": "Radiofrequency energy flow per unit area — µW/m² on consumer RF meters, mW/cm² in FCC rules, W/m² in ICNIRP guidelines. 1 mW/cm² = 10 W/m² = 10,000,000 µW/m².",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "S",
          "power flux density",
          "µW/m²",
          "mW/cm²"
        ],
        "quantityId": "power-density",
        "symbol": "S",
        "siUnit": "W/m²",
        "units": [
          {
            "symbol": "W/m²",
            "name": "watt per square metre",
            "toBase": 1
          },
          {
            "symbol": "mW/m²",
            "name": "milliwatt per square metre",
            "toBase": 0.001
          },
          {
            "symbol": "µW/m²",
            "name": "microwatt per square metre",
            "toBase": 0.000001
          },
          {
            "symbol": "mW/cm²",
            "name": "milliwatt per square centimetre",
            "toBase": 10
          },
          {
            "symbol": "µW/cm²",
            "name": "microwatt per square centimetre",
            "toBase": 0.01
          }
        ],
        "measures": "Radiofrequency exposure in the far field. The single most confused quantity in EMF discussion, because regulators, guideline bodies and consumer meters each prefer a different unit and differ by factors of 10,000 or more.",
        "conversions": [
          {
            "to": "electric-field-strength",
            "formula": "E (V/m) = √(S (W/m²) × 377)",
            "note": "Far-field relation. 1 V/m ≈ 2653 µW/m²; 6 V/m ≈ 95,500 µW/m²; 61 V/m ≈ 10 W/m²."
          },
          {
            "to": "power-density",
            "formula": "S = EIRP / (4πd²)",
            "note": "Free-space power density at distance d from an isotropic radiator of a given equivalent isotropically radiated power. Ignores reflections, absorption and antenna pattern, so it is an upper-bound estimate on boresight and an over-estimate elsewhere."
          }
        ],
        "related": [
          "limits:fcc-mpe-public-1500-100000",
          "limits:sbm-2024-rf-no-anomaly"
        ]
      },
      "sources": [
        {
          "id": "nist-si",
          "title": "The International System of Units (SI), NIST Special Publication 330",
          "publisher": "National Institute of Standards and Technology",
          "url": "https://www.nist.gov/pml/special-publication-330",
          "kind": "government",
          "retrieved": "2026-08-12"
        },
        {
          "id": "itu-fs-relations",
          "title": "Free-space path loss and power density relations (ITU-R P.525)",
          "publisher": "International Telecommunication Union",
          "url": "https://www.itu.int/rec/R-REC-P.525/en",
          "kind": "standard",
          "retrieved": "2026-08-12"
        },
        {
          "id": "fcc-1310",
          "title": "47 CFR § 1.1310 — Radiofrequency radiation exposure limits",
          "publisher": "U.S. Government Publishing Office (eCFR)",
          "url": "https://www.ecfr.gov/current/title-47/section-1.1310",
          "kind": "regulation",
          "retrieved": "2026-08-12"
        },
        {
          "id": "icnirp-2020",
          "title": "Guidelines for Limiting Exposure to Electromagnetic Fields (100 kHz to 300 GHz)",
          "publisher": "International Commission on Non-Ionizing Radiation Protection",
          "url": "https://www.icnirp.org/en/publications/article/rf-guidelines-2020.html",
          "year": 2020,
          "kind": "guideline",
          "retrieved": "2026-08-12"
        }
      ],
      "links": {
        "self": "https://emfbase.com/api/quantities/power-density",
        "html": "https://emfbase.com/quantities/power-density",
        "markdown": "https://emfbase.com/quantities/power-density.md",
        "collection": "https://emfbase.com/api/quantities"
      }
    },
    {
      "id": "quantities:specific-absorption-rate",
      "collection": "quantities",
      "slug": "specific-absorption-rate",
      "name": "Specific absorption rate (SAR)",
      "summary": "Watts of RF power absorbed per kilogram of tissue — the dosimetric quantity behind phone compliance testing, limited to 1.6 W/kg over 1 g in the U.S. and 2 W/kg over 10 g under ICNIRP.",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "SAR",
          "W/kg"
        ],
        "quantityId": "specific-absorption-rate",
        "symbol": "SAR",
        "siUnit": "W/kg",
        "units": [
          {
            "symbol": "W/kg",
            "name": "watt per kilogram",
            "toBase": 1
          },
          {
            "symbol": "mW/g",
            "name": "milliwatt per gram",
            "toBase": 1
          },
          {
            "symbol": "mW/kg",
            "name": "milliwatt per kilogram",
            "toBase": 0.001
          }
        ],
        "measures": "Energy absorption in tissue during near-field exposure, measured in a liquid-filled phantom at maximum transmit power. Because the U.S. averages over 1 g and ICNIRP over 10 g, the two published numbers for the same phone are not comparable.",
        "related": [
          "limits:fcc-sar-partial-body",
          "limits:icnirp-2020-sar-local"
        ]
      },
      "sources": [
        {
          "id": "fcc-2-1093",
          "title": "47 CFR § 2.1093 — Radiofrequency radiation exposure evaluation: portable devices",
          "publisher": "U.S. Government Publishing Office (eCFR)",
          "url": "https://www.ecfr.gov/current/title-47/section-2.1093",
          "kind": "regulation",
          "retrieved": "2026-08-12"
        },
        {
          "id": "icnirp-2020",
          "title": "Guidelines for Limiting Exposure to Electromagnetic Fields (100 kHz to 300 GHz)",
          "publisher": "International Commission on Non-Ionizing Radiation Protection",
          "url": "https://www.icnirp.org/en/publications/article/rf-guidelines-2020.html",
          "year": 2020,
          "kind": "guideline",
          "retrieved": "2026-08-12"
        }
      ],
      "links": {
        "self": "https://emfbase.com/api/quantities/specific-absorption-rate",
        "html": "https://emfbase.com/quantities/specific-absorption-rate",
        "markdown": "https://emfbase.com/quantities/specific-absorption-rate.md",
        "collection": "https://emfbase.com/api/quantities"
      }
    },
    {
      "id": "quantities:body-voltage",
      "collection": "quantities",
      "slug": "body-voltage",
      "name": "Body voltage",
      "summary": "Millivolts induced on a person by nearby power-frequency electric fields, measured against a ground reference; the metric building biologists use to judge bedroom wiring.",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "body voltage measurement",
          "mV body voltage"
        ],
        "quantityId": "body-voltage",
        "symbol": "U",
        "siUnit": "V",
        "units": [
          {
            "symbol": "V",
            "name": "volt",
            "toBase": 1
          },
          {
            "symbol": "mV",
            "name": "millivolt",
            "toBase": 0.001
          }
        ],
        "measures": "Capacitive coupling between household wiring and the body. It is a proxy for the local AC electric field and depends strongly on grounding method, so readings are only comparable when the protocol is identical.",
        "related": [
          "limits:sbm-2024-electric-bands",
          "protocols:body-voltage-survey"
        ]
      },
      "sources": [
        {
          "id": "sbm-2024",
          "title": "Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024)",
          "publisher": "Institut für Baubiologie + Nachhaltigkeit (IBN)",
          "url": "https://buildingbiology.com/site/downloads/SBM-2024_EVALUATION_GUIDELINES_EN.pdf",
          "year": 2024,
          "kind": "ngo",
          "retrieved": "2026-08-12"
        }
      ],
      "links": {
        "self": "https://emfbase.com/api/quantities/body-voltage",
        "html": "https://emfbase.com/quantities/body-voltage",
        "markdown": "https://emfbase.com/quantities/body-voltage.md",
        "collection": "https://emfbase.com/api/quantities"
      }
    },
    {
      "id": "quantities:attenuation",
      "collection": "quantities",
      "slug": "shielding-attenuation",
      "name": "Shielding attenuation",
      "summary": "Decibels of field reduction provided by a material. Every 10 dB is a factor of 10 in power density: 30 dB removes 99.9%, 10 dB removes 90%.",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "dB attenuation",
          "shielding effectiveness"
        ],
        "quantityId": "attenuation",
        "symbol": "A",
        "siUnit": "dB",
        "units": [
          {
            "symbol": "dB",
            "name": "decibel",
            "toBase": 1
          }
        ],
        "measures": "Ratio of incident to transmitted field, band-dependent and geometry-dependent. Manufacturer dB figures are measured on flat samples in a test fixture; installed performance is usually lower because of seams, edges and reflections.",
        "conversions": [
          {
            "to": "power-density",
            "formula": "S_after = S_before / 10^(dB/10)",
            "note": "For field strength in V/m the divisor is 10^(dB/20)."
          }
        ]
      },
      "sources": [
        {
          "id": "nist-si",
          "title": "The International System of Units (SI), NIST Special Publication 330",
          "publisher": "National Institute of Standards and Technology",
          "url": "https://www.nist.gov/pml/special-publication-330",
          "kind": "government",
          "retrieved": "2026-08-12"
        }
      ],
      "links": {
        "self": "https://emfbase.com/api/quantities/shielding-attenuation",
        "html": "https://emfbase.com/quantities/shielding-attenuation",
        "markdown": "https://emfbase.com/quantities/shielding-attenuation.md",
        "collection": "https://emfbase.com/api/quantities"
      }
    },
    {
      "id": "quantities:frequency",
      "collection": "quantities",
      "slug": "frequency",
      "name": "Frequency",
      "summary": "Cycles per second, the axis that determines which limit applies, which meter can see the signal, and which shielding works.",
      "status": "verified",
      "lastVerified": "2026-08-12",
      "data": {
        "aliases": [
          "Hz",
          "GHz",
          "MHz"
        ],
        "quantityId": "frequency",
        "symbol": "f",
        "siUnit": "Hz",
        "units": [
          {
            "symbol": "Hz",
            "name": "hertz",
            "toBase": 1
          },
          {
            "symbol": "kHz",
            "name": "kilohertz",
            "toBase": 1000
          },
          {
            "symbol": "MHz",
            "name": "megahertz",
            "toBase": 1000000
          },
          {
            "symbol": "GHz",
            "name": "gigahertz",
            "toBase": 1000000000
          }
        ],
        "measures": "Signal repetition rate. EMF work splits at roughly 100 kHz: below it, effects and limits are about nerve stimulation and fields are treated as electric and magnetic separately; above it, limits are about energy absorption and the two components are linked."
      },
      "sources": [
        {
          "id": "nist-si",
          "title": "The International System of Units (SI), NIST Special Publication 330",
          "publisher": "National Institute of Standards and Technology",
          "url": "https://www.nist.gov/pml/special-publication-330",
          "kind": "government",
          "retrieved": "2026-08-12"
        },
        {
          "id": "icnirp-2020",
          "title": "Guidelines for Limiting Exposure to Electromagnetic Fields (100 kHz to 300 GHz)",
          "publisher": "International Commission on Non-Ionizing Radiation Protection",
          "url": "https://www.icnirp.org/en/publications/article/rf-guidelines-2020.html",
          "year": 2020,
          "kind": "guideline",
          "retrieved": "2026-08-12"
        }
      ],
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    }
  ]
}