EIRP Calculator — Effective Isotropic Radiated Power
EIRP quantifies the total apparent radiated power of an antenna system in its peak direction. Enter transmitter power, antenna gain, and cable/connector loss to get EIRP in dBm, dBW, and milliwatts.
dBm
dBi
dB
m
446,7 mW • -3,5 dBW
- 1
Net antenna gain after cable loss
8 − 1,5 = 6,5Antenna gain (dBi) minus feed-line and connector losses (dB). - 2
EIRP
20 + 6,5 = 26,50
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EIRP (dBm) = transmitter power (dBm) + antenna gain (dBi) − cable loss (dB). Convert to watts with EIRP_W = 10^((EIRP_dBm − 30)/10). EIRP captures the effective radiated power in the antenna's peak direction; regulatory bodies set maximum EIRP limits for licence-exempt bands such as 20 dBm (100 mW) for 2.4 GHz Wi-Fi in Europe.
Wzór
How this is calculated
EIRP (Effective Isotropic Radiated Power) represents the hypothetical power that a perfect isotropic radiator would need to produce the same signal strength as the actual antenna system in its maximum-gain direction. It combines three quantities on the decibel scale: the transmitter's output power, the antenna's gain over an isotropic reference (dBi), and any power lost in the feed cable and connectors between them.
Because decibels are logarithmic, the combination is simple arithmetic: EIRP = Tx_power_dBm + gain_dBi − cable_loss_dB. Converting to watts uses the standard formula W = 10^((EIRP_dBm − 30) / 10). Power density at distance d is then EIRP_W / (4π × d²) assuming free-space propagation with no reflections, absorbers, or beam directivity effects — useful for estimating EMF exposure or link-budget margins.
Regulatory authorities set maximum EIRP limits for licence-exempt bands. For example, the European ETSI EN 300 328 standard caps 2.4 GHz Wi-Fi access points at 100 mW EIRP (20 dBm), and many 5 GHz channels are limited to 200 mW EIRP (23 dBm). Always verify local regulations before deploying high-gain antenna systems.
Najczęściej zadawane pytania
EIRP (Effective Isotropic Radiated Power) references a perfect isotropic radiator, while ERP (Effective Radiated Power) references a half-wave dipole, which has 2.15 dBi of inherent gain. Therefore ERP = EIRP − 2.15 dB. Broadcast regulations often specify limits in ERP, while Wi-Fi and most modern standards use EIRP.
Every metre of coaxial cable dissipates a fraction of the RF power as heat. At 2.4 GHz, a typical RG-58 cable loses about 1 dB per 3 metres, meaning roughly 20 % of the transmitter's power never reaches the antenna. Minimising cable length or using low-loss cable (LMR-400, etc.) directly increases EIRP and range.
Yes — EIRP always refers to the peak-gain direction of the antenna. A 15 dBi Yagi pointed at a target has the same EIRP in that direction as a perfect sphere radiating from all sides with the same total power. In non-peak directions, the effective radiated power is lower according to the antenna's radiation pattern.
Znany również jako
TG we-Calculate Editorial Team. (2026). EIRP Calculator — Effective Isotropic Radiated Power [Online calculator]. TG we-Calculate. https://we-calculate.com/pl/calculator/eirp-calculator
TG we-Calculate Editorial Team. "EIRP Calculator — Effective Isotropic Radiated Power." TG we-Calculate. 2026. https://we-calculate.com/pl/calculator/eirp-calculator.
TG we-Calculate Editorial Team, "EIRP Calculator — Effective Isotropic Radiated Power," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/pl/calculator/eirp-calculator
@misc{wecalculate_eirp_calculator, title = {EIRP Calculator — Effective Isotropic Radiated Power}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/pl/calculator/eirp-calculator}}, year = {2026}, note = {TG we-Calculate} }
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