Estimate how a device might fare in an EMP or solar-storm event
A transparent, citation-backed scoring model covering two distinct threats: a nuclear electromagnetic pulse (distance, shielding, circuitry, grid connection) and a solar geomagnetic storm (NOAA storm intensity, your geomagnetic latitude, and long-conductor coupling). Every coefficient is documented — see methodology for sourcing and limits.
Scenario Inputs
Approximate geomagnetic (not geographic) latitude. Portland, OR and most of the northern US fall in the Mid band.
Risk Profile
Driver breakdown
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This score reflects a simplified heuristic model of published EMP waveform and shielding data — treat it as a comparative planning aid, not a probability guarantee for any real event.
Vulnerability lookup table
Baseline vulnerability ratings for common household and everyday devices, assuming no shielding and each device's typical real-world circuitry and connection profile. Click any row to load it into the calculator above.
| Device | Category | Circuitry | Connection | Baseline vulnerability |
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Methodology & sources
Distance falloff
Field intensity is modeled as a piecewise curve with a near-field plateau inside ~3 miles, a steep drop through 3–8 miles, and a long shallow tail beyond 20 miles — matching the qualitative falloff described for surface-burst EMP deposition zones.
Glasstone & Dolan, "The Effects of Nuclear Weapons," Ch. XI HHS REMM — EMP Following a Nuclear Detonation U.S. Army FM 3-3-1, Appendix C — SBEMP rangesFaraday shielding attenuation
Shielding tiers use decibel attenuation values converted to a linear field-ratio multiplier (10^(−dB/20)): unshielded (0dB), foil wrap (~25dB), improvised metal enclosure (~45dB), and welded mil-spec cage (~85dB, referencing the MIL-STD-188-125 80dB benchmark).
Seasoned Citizen Prepper — DIY Faraday Cage shielding tiers Salt & Prepper — Faraday Cage Construction, dB reference table Science Insights — measured shielding by materialCircuitry vulnerability factor
Modern dense solid-state electronics are weighted as most vulnerable; older discrete/mixed solid-state as intermediate; purely electromechanical, mechanical, or vacuum-tube designs as comparatively robust, consistent with EMP Commission findings on semiconductor miniaturization.
Wikipedia — Nuclear electromagnetic pulse, device susceptibility Report of the Commission to Assess the Threat to the United States from EMP AttackSolar storm (geomagnetic / GIC) scenario
Storm severity uses NOAA's G-scale (G1–G5, tied to the planetary Kp index) and a geomagnetic-latitude multiplier — higher-numbered storms extend disruptive currents to progressively lower geomagnetic latitudes. Unlike nuclear EMP's fast radiated E1 pulse, a geomagnetic storm induces a slow current (GIC) that couples almost exclusively through long grounded conductors — mains wiring, pipelines, transmission lines — so isolated battery electronics are modeled as largely unaffected even in an extreme (G5) event. Faraday shielding is a radiated-field countermeasure and only partially applies here; the calculator discounts its effect accordingly and explains this directly in the shielding recommendation card.
NOAA Space Weather Prediction Center — G-scale definitions and grid effects SpaceWeatherLive — Kp index to G-scale and geomagnetic latitude mapping EEI / EPRI — grid security and E3/GIC key findings SpaceNews — May 2024 G5 storm vs. 1859 Carrington Event severityGrid / conductor coupling
Devices attached to long conductors — mains wiring, vehicle harnesses, exterior antennas, or telephone lines — receive a coupling multiplier reflecting their role as effective E1/E2/E3 collector structures, versus battery-isolated devices with only short internal traces.
Spilma — HEMP/IEMI waveform components (E1/E2/E3) and coupling Congressional Research Service — Grid Resilience Against EMP (R47339) JCIP — Automotive Ground Vehicles' HEMP Resilience (ECU harness coupling)How this compares to other calculators
Most public EMP/nuclear tools model a different layer of the problem than this one. Blast, fallout, and yield-based tools (FAS, MIT's Nuclear Weapons Education Project, NukeMap-style simulators) compute geographic destruction and radiation zones, not electronics failure. EMP-radius calculators return a single ground-footprint distance from yield and burst altitude, with no per-device modeling. The closest consumer-facing tool, AcreTools' EMP Prep Calculator, covers similar ground — Faraday sizing, grid exposure, vehicle age — but produces a qualitative readiness score rather than a distance/shielding-dB/circuitry/grid probability model with an uncertainty band. This tool is, to our knowledge, the only public calculator that combines all four factors into a single per-device failure probability.
AcreTools — EMP Prep Calculator (closest comparable: Faraday sizing + qualitative readiness score) Calculator Academy — EMP Radius Calculator (yield/altitude ground-footprint only) Federation of American Scientists — Nuclear Weapon Effects Calculator (blast/thermal/radiation, not EMP) MIT Nuclear Weapons Education Project — effects simulators & modelsLimits of this model
Real HEMP/EMP outcomes depend on burst altitude and yield, geomagnetic latitude, precise device design margins, cable geometry, and manufacturing tolerance — factors this tool cannot observe. The EMP Commission and independent researchers note no consensus exists on exact damage thresholds for consumer electronics. Treat every output as an order-of-magnitude planning signal, not a certified survivability guarantee, and always maintain redundant non-electronic backups for critical functions.