Calculate Effective Isotropic Radiated Power from transmitter power, antenna gain, and cable losses with link budget and power density analysis.
The EIRP (Effective Isotropic Radiated Power) calculator determines the total radiated power in the direction of maximum antenna gain, accounting for transmitter output power, antenna gain, and cable/connector losses. EIRP is the fundamental parameter in RF link budget analysis and regulatory compliance.
EIRP represents the power that would need to be fed to a hypothetical isotropic antenna (radiating equally in all directions) to produce the same signal strength in the direction of maximum gain as the actual antenna system. It combines transmitter power (in dBm or watts), antenna gain (in dBi), and feed system losses (cable, connectors, filters) into a single figure that describes the system's radiated performance.
Telecommunications engineers, amateur radio operators, and wireless system designers use EIRP for link budget calculations, regulatory compliance verification, RF safety assessments, and coverage planning. This calculator supports multiple power and gain units, computes both EIRP and ERP, and provides a complete link budget showing received power and power density at various distances.
EIRP calculation is essential for RF system design, from Wi-Fi access points and cellular base stations to satellite communications and amateur radio. This calculator simplifies link budget analysis by combining transmitter power, antenna gain, and losses into EIRP, then projecting signal strength at various distances. It's indispensable for compliance verification and coverage planning.
EIRP (dBm) = P_tx (dBm) + G_antenna (dBi) − L_cable (dB). ERP (dBm) = EIRP − 2.15 dB. FSPL (dB) = 20·log₁₀(d) + 20·log₁₀(f) − 147.55 where d is in meters and f is in Hz. Power density S = EIRP / (4πd²).
Result: 55.0 dBm EIRP (316.2 W)
100 W = 50 dBm. With 6 dBi antenna gain minus 1 dB cable loss: EIRP = 50 + 6 − 1 = 55 dBm = 316.2 W. At 1 km and 900 MHz, FSPL ≈ 91.5 dB, giving received power of −36.5 dBm.
Use consistent units, verify assumptions, and document conversion standards for repeatable outcomes.
Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use. ## Practical Notes
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Track units and conversion paths before applying the result. ## Practical Notes
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EIRP references an isotropic antenna, while ERP references a half-wave dipole. ERP = EIRP − 2.15 dB, since a dipole has 2.15 dBi gain.
Most countries limit EIRP for each frequency band to prevent interference. For example, Wi-Fi is typically limited to 36 dBm (4 W) EIRP in many regions.
dBi is gain relative to an isotropic (point) radiator. dBd is gain relative to a dipole antenna. dBi = dBd + 2.15.
Cable loss directly reduces EIRP watt-for-watt. At microwave frequencies, even short cable runs can lose several dB, so keeping cables short and using low-loss types is critical.
FSPL is the signal attenuation due to the geometric spreading of the electromagnetic wave, following the inverse square law. It increases with both frequency and distance.
Higher EIRP extends coverage range, but the relationship is logarithmic. Doubling EIRP (+3 dB) extends range by only about 41% in free space.