Power Calculator
Interactive tool to calculate ERP and EIRP, check compliance with ANACOM limits, and test different combinations of power, gain, and losses.
Inputs
ANACOM limits
dB
dB
If the gain is in dBd, we automatically convert to dBi (+2.15 dB).
Results
EIRP
— dBm
— mW (— W)
ERP (referenced to dipole)
— dBm
— mW (— W)
Compliance (limit 10 dBm)
—
Definitions
EIRP - Effective Isotropic Radiated Power (Effective Isotropic Radiated Power)
ERP - Effective Radiated Power (Effective Radiated Power)
EIRP uses antenna gain in dBi (decibel relative to isotropic).
ERP uses antenna gain in dBd (decibel relative to dipole).
Practical examples (433 MHz and 868 MHz)
Click Load into form to test the values.
433 MHz
6 dBi antenna, cable losses 0 dB
Pt = 4 dBm · Lc = 0 dB · Ga = 6 dBi
EIRP = 10 dBm · ERP = 7.85 dBm
2.15 dBi dipole, no losses
Pt = 7.5 dBm · Lc = 0 dB · Ga = 2.15 dBi
EIRP = 9.65 dBm · ERP = 7.5 dBm
5 dBi antenna, cable losses 1 dB
Pt = 6 dBm · Lc = 1 dB · Ga = 5 dBi
EIRP = 10 dBm · ERP = 7.85 dBm
868 MHz
6.5 dBi antenna, cable losses 1.5 dB
Pt = 22 dBm · Lc = 1.5 dB · Ga = 6.5 dBi
EIRP = 27 dBm · ERP = 24.85 dBm
2.15 dBi dipole, no losses
Pt = 22 dBm · Lc = 0 dB · Ga = 2.15 dBi
EIRP = 24.15 dBm · ERP = 22 dBm
5 dBi antenna, cable losses 1 dB
Pt = 22 dBm · Lc = 1 dB · Ga = 5 dBi
EIRP = 26 dBm · ERP = 23.85 dBm
ANACOM — Station License Exemption (02 Jan 2025)
Non-specific short-range equipment (includes LoRa applications).
433 MHz
433.050-434.790 MHz
Max ERP: 10 mW (10 dBm)
Duty cycle: 10%
868 MHz
869.400-869.650 MHz
Max ERP: 500 mW (27 dBm)
Duty cycle: 10%
Common LoRa transceivers: SX1276 (20 dBm / 100 mW), SX1262/LR1110 (22 dBm / 160 mW). Power adjusted by software.
Terminology and conversions
EIRP uses dBi; ERP uses dBd.
dBd = dBi - 2.15 dB · ERP = EIRP - 2.15 dB