EIRP Calculator

Estimate effective isotropic radiated power (EIRP) and compliance headroom in dBm and watts.

dBi
m
dB/m
dB
dBm
MHz
km
dBi

Quick Facts

EIRP Meaning
Radiated equivalent power
Combines TX power, gain, and losses
dBm to Watts
10^(dBm/10)/1000
Useful for equipment datasheets
Compliance Margin
Limit - EIRP
Negative means over limit
Typical Failure
Ignoring losses
Small loss assumptions change compliance outcome

EIRP & Compliance

RF Result
EIRP
0 dBm
Main compliance metric
EIRP (Watts)
0 W
Linear power equivalent
Compliance Margin
0 dB
Positive is below limit
Estimated RX Power
0 dBm
EIRP - FSPL + RX gain

Link Budget Components

Key Takeaways

  • EIRP is the regulatory metric used in many RF systems, not raw transmitter power alone.
  • Antenna gain increases EIRP while cable and connector losses reduce it.
  • Compliance should be checked in worst-case operating conditions, not nominal assumptions.

How EIRP Is Computed

Effective isotropic radiated power combines transmitter output, antenna gain, and system losses. This calculator helps you run quick compliance checks without manual dB conversions.

This eirp calculator page is designed for practical planning, not just one-off math. Real outcomes are usually driven by multiple interacting variables, so using a structured calculator helps you model assumptions transparently and make better decisions.

For best results, run a baseline case first and then compare at least one conservative and one aggressive scenario. That comparison gives you a realistic range and highlights which assumptions have the largest impact on the outcome.

Use the outputs as decision support for pacing, resource allocation, and checkpoint planning. Recalculate whenever your underlying assumptions change so your plan remains aligned with current conditions.

EIRP(dBm) = TX + TX gain - feeder/connector losses; FSPL(dB) = 32.44 + 20log10(MHz) + 20log10(km)
RX Estimate: RX(dBm) ≈ EIRP - FSPL + RX antenna gain.

Example Scenario

With 30 dBm TX, 12 dBi antenna gain, and 3.3 dB total loss, EIRP is 38.7 dBm before any further attenuation.

Practical Insight

Small gain increases can quickly exceed legal limits in unlicensed bands.

Pro Tip

Model maximum-power firmware state and lowest-loss cable condition for conservative compliance checks.

How to Use This Calculator Effectively

  1. Enter TX output, antenna gain, and feeder characteristics.
  2. Provide connector losses and regulatory EIRP limit.
  3. Add frequency, distance, and RX gain for a rough received-power estimate.
  4. Review compliance margin and adjust gain/power if needed.

Input Strategy and Assumptions

Validate assumptions before acting on outputs. Unit mismatches and unrealistic baselines are the most common causes of planning error.

  • Keep units consistent across all inputs and supporting documents.
  • Use data from the same time horizon as your planning decision.
  • Include practical constraints rather than ideal-case assumptions only.
  • When uncertain, start conservative and document why.

How to Interpret the Results

Treat outputs as planning guidance and ranges. The strongest value comes from comparing scenarios and updating assumptions over time.

  • Use the highlighted output card as the primary planning anchor.
  • Review supporting metrics to test whether execution is realistic.
  • Large baseline-to-adjusted gaps usually indicate high sensitivity.
  • Recalculate after meaningful changes in context or constraints.

Scenario Planning Framework

A simple scenario process makes this calculator much more useful for operational decisions.

  1. Run a baseline scenario using your current assumptions.
  2. Run a conservative scenario with higher friction.
  3. Run an upside scenario with optimized assumptions.
  4. Define decision thresholds and update triggers from the spread.

Implementation Checklist

  • Confirm units and assumptions before sharing outputs.
  • Document baseline, conservative, and upside scenarios.
  • Translate outputs into concrete actions and checkpoints.
  • Schedule a refresh date for recalculation.

Common Mistakes to Avoid

  • Treating dBi antenna gain as optional in compliance calculations.
  • Ignoring connector and jumper losses.
  • Comparing watts directly without dBm conversion consistency.

Frequently Asked Questions

Antenna gain increases directional power density, raising EIRP above TX output.

No. Negative margin indicates you exceed the configured regulatory limit.

Yes. Cable, connector, and filter losses all affect final EIRP.