Speaker Current Calculator

This tool finds the current consumption of a speaker (in Amperes or simply Amps). This is used to determine the cable thickness and specifications for the relay.


  • Power rating of the amplifier driving the speaker (P)
  • Speaker Impedance (R)


I = √ (P/R)

Example Calculation

Consider an amplifier that’s rated for 50 Watt RMS (Root-mean-square) driving a speaker with an impedance of 8 ohm. In this case the current drawn by the speaker will be 2.5 Amps.

Note that while the amplifier might be rated for a certain power level, it is not always delivering this much power. As a result the current consumption will typically be lower than the max number that this calculator provides.

Related Calculators

  • Speaker Impedance – calculate the impedance of speakers in either parallel or series configuration