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Calcimator

SWR Power Loss Calculator

Calculate percentage of power lost from SWR mismatch. Shows reflected power, mismatch loss, additional feedline loss, and power delivered to antenna.

Inputs

W
dB

Results

Power to Antenna

66.66 W

≈ 7 LED bulbs

Power Reflected

11.11 W

System Efficiency

66.7 %

Power Reflected11.1 %
Mismatch Loss0.512 dB
Extra Feedline Loss (SWR)0.25 dB
Total System Loss1.76 dB
Safe for RigYes
How to Use This Calculator
  1. Enter your measured SWR from your antenna analyzer or transmitter's built-in meter.
  2. Set transmit power (W) and matched feedline loss (dB per 100 ft at your frequency).
  3. Review power delivered to the antenna, power reflected (W and %), and total mismatch loss (dB).
  4. Check additional feedline loss due to SWR — high SWR significantly increases cable losses.
  5. Use the results to decide if an antenna tuner or antenna adjustment is warranted.

How the result changes with Transmit Power

Transmit PowerPower to AntennaPower ReflectedSystem Efficiency
15099.99 W16.67 W66.7 %
525349.95 W58.33 W66.7 %
975649.91 W108.33 W66.7 %
1,350899.87 W150 W66.7 %

What each input means

SWR
Standing wave ratio reading from SWR meter or antenna analyzer
Transmit Power
Transmitter output power in watts
Matched Feedline Loss
Feedline loss when perfectly matched (from coax cable loss calculator)

How this is calculated

Formula

Γ = (SWR-1)/(SWR+1); Reflected% = Γ² × 100

Worked example, using the default values

  1. Identify Input Parameters
    SWR = 2, Transmit Power = 100, Matched Feedline Loss = 1 = 3 input(s) provided
  2. Calculate Power to Antenna
    Power to Antenna
    66.66 = 66.66
  3. Calculate Power Reflected
    Power Reflected
    11.11 = 11.11
  4. Calculate System Efficiency
    System Efficiency
    66.7 = 66.7
  5. Calculate Power Reflected
    Power Reflected
    11.1 = 11.1
  6. Calculate Mismatch Loss
    Mismatch Loss
    0.512 = 0.512

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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