📡 EIRP Calculator
Calculate Effective Isotropic Radiated Power
How to Use This Calculator
Enter Transmit Power
Input the transmitter output power in decibels relative to milliwatts (dBm). This is the power output from your radio or transmitter. Typical values range from 10-30 dBm (10 mW to 1 W).
Enter Antenna Gain
Enter the antenna gain in decibels relative to an isotropic antenna (dBi). This value is typically provided in antenna specifications. Common values range from 2-20 dBi depending on antenna type.
Enter Cable Loss (Optional)
Enter any cable or connector losses in decibels (dB). If you have no losses, enter 0. Typical cable losses range from 0.1-3 dB depending on cable length and quality.
Calculate EIRP
Click the "Calculate" button to compute the Effective Isotropic Radiated Power. The result will be displayed in both dBm and Watts for your convenience.
About EIRP Calculator
The EIRP (Effective Isotropic Radiated Power) Calculator computes the equivalent power that would need to be radiated from an isotropic antenna to achieve the same signal strength as your directional antenna system. EIRP is a critical parameter in radio frequency (RF) engineering, wireless communications, and regulatory compliance.
When to Use This Calculator
- RF System Design: Calculate EIRP for wireless communication systems
- Regulatory Compliance: Ensure your system meets FCC, ETSI, or other regulatory limits
- Antenna Selection: Determine appropriate antenna gain for desired coverage
- Link Budget Analysis: Calculate total radiated power for path loss calculations
- Wi-Fi Planning: Design wireless networks within legal power limits
Why Use Our Calculator?
- ✅ Dual Units: Provides results in both dBm and Watts
- ✅ Cable Loss Accounting: Includes cable losses in calculations
- ✅ Regulatory Compliance: Helps ensure compliance with power limits
- ✅ Accurate Calculations: Uses standard RF engineering formulas
- ✅ Free to Use: No registration or payment required
Understanding EIRP
EIRP represents the total power radiated by your antenna system, accounting for transmitter power, antenna gain, and any losses. It's measured as if the power were radiated equally in all directions (isotropic). Higher EIRP means stronger signals and longer range, but must comply with regulatory limits. EIRP is typically expressed in dBm or Watts, with common values ranging from 20-40 dBm (100 mW to 10 W) for most applications.
Formula
EIRP = P_tx + G_ant - L_cable
(all values in dB)
Where:
- EIRP = Effective Isotropic Radiated Power (dBm)
- P_tx = Transmit Power (dBm)
- G_ant = Antenna Gain (dBi)
- L_cable = Cable/Connector Losses (dB)
Example Calculation:
For a system with transmit power = 20 dBm, antenna gain = 10 dBi, and cable loss = 2 dB:
EIRP = 20 + 10 - 2
EIRP = 28 dBm
EIRP = 631 mW (0.631 W)
Note: To convert dBm to Watts: P(W) = 10^((dBm - 30)/10)
Frequently Asked Questions
What is EIRP and why is it important?
EIRP (Effective Isotropic Radiated Power) measures the total power radiated by an antenna system, accounting for transmitter power, antenna gain, and losses. It's critical for regulatory compliance, link budget calculations, and ensuring your system operates within legal power limits while maximizing signal strength.
What's the difference between EIRP and ERP?
EIRP (Effective Isotropic Radiated Power) is referenced to an isotropic antenna (radiates equally in all directions), while ERP (Effective Radiated Power) is referenced to a half-wave dipole antenna. EIRP = ERP + 2.15 dB, since a dipole has 2.15 dBi gain over isotropic. Most regulations specify EIRP limits.
How do I convert between dBm and Watts?
To convert dBm to Watts: P(W) = 10^((dBm - 30)/10). For example, 30 dBm = 1 W, 20 dBm = 0.1 W, 40 dBm = 10 W. To convert Watts to dBm: dBm = 10×log₁₀(P(W)) + 30.
What are typical EIRP limits for different applications?
FCC limits vary by band: 2.4 GHz Wi-Fi typically allows 36 dBm (4 W) EIRP, 5 GHz Wi-Fi allows up to 36 dBm indoors, cellular base stations can be much higher. Always check your local regulations for specific limits in your frequency band and location.
Should I include cable losses in my EIRP calculation?
Yes, always include cable and connector losses. These reduce the effective power reaching the antenna, so they must be subtracted from your total EIRP. Typical losses range from 0.1-3 dB depending on cable type, length, and quality. Omitting losses can cause you to exceed regulatory limits.