EIRP & ERP
Calculate equivalent radiated power from conducted power, feed losses and antenna gain.
Power at your reference point, before the losses entered below.
Use ordinary gain: it includes radiation efficiency, but excludes antenna mismatch.
Feed & mismatch losses 0 dB
One-way loss from the power reference point to the antenna port.
Incident-to-accepted power reduction. Enter 0 if already included in your power input.
EIRP · isotropic reference
2.15 dBm
1.64 mW
- ERP · half-wave dipole reference
- 0 dBm
- Accepted antenna power
- 0 dBm
EIRP = ERP + 2.15 dB. These compare radiation in the gain direction; they are not total radiated power.
Power reference: Transmitter output connector
Gain direction: Boresight
More measurements
Conducted power for a target
- Required conducted power
- 27.85 dBm
Reference point: Transmitter output connector. Uses the gain and losses above. Set transfers the result to the power input.
Reference point & direction
These notes identify your calculation; they do not change its power convention. If your power input is already accepted by the antenna, enter zero feed and mismatch losses.
Power accounting
- Conducted power · starting level
- 0 dBm
- Subtract feed / connector loss
- 0 dB
- Power after feed loss
- 0 dBm
- Subtract antenna mismatch loss
- 0 dB
- Accepted antenna power
- 0 dBm
- Add directional antenna gain
- 2.15 dBi
- EIRP · final level
- 2.15 dBm
Negative gain lowers the directional equivalent level. dBi uses an isotropic reference; dBd uses a half-wave dipole reference, so gain in dBi = gain in dBd + 2.15 dB.
Watts & dBW equivalents
- EIRP
- 1.64 mW
- -27.85 dBW
- ERP
- 1 mW
- -30 dBW
- Accepted antenna power
- 1 mW
- -30 dBW
Generated values display at most two decimals. Calculations and copies retain full precision until edited.
Model & assumptions
Begin with conducted forward power at the feed input. Subtract feed loss and antenna mismatch loss to find the power accepted by the antenna:
Both powers are in dBm; losses are non-negative dB magnitudes. If the entered power is already the accepted antenna power, set these upstream losses to zero.
EIRP is the isotropic-antenna power that would produce the same power density in the chosen direction. Add ordinary directional antenna gain to accepted power:
The result is in dBm. Ordinary gain includes radiation efficiency but excludes mismatch. Realized gain already includes mismatch, so using it here and subtracting mismatch loss would count that loss twice.
ERP uses a half-wave dipole as its reference instead of an isotropic antenna. That changes the equivalent power level by 2.15 dB:
ERP is also in dBm here. For antenna gain, add 2.15 to convert dBd to dBi. Keep frequency, direction, averaging and power reference points consistent. These directional equivalents are not total radiated power or regulatory pass/fail results. Multiple reflections are excluded; the target-power calculation holds gain and losses fixed.
Generated values from unit or reference changes and Set conducted power show at most two decimals while retaining full precision for the forward and target calculations and copied inputs until edited. The watt value below EIRP is the same isotropic-reference directional equivalent expressed in linear units.
For example, 30 dBm minus 3 dB feed loss and 1 dB mismatch loss gives 26 dBm accepted power. A gain of 6 dBd (8.15 dBi) gives 34.15 dBm EIRP and 32 dBm ERP.
Does a result look wrong? Report a calculation issue
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