Audio Watt Meter

How do you measure the power output of an amplifier? using an Audio Wattmeter. the name Audio Watt Meter’ is a collective name for all devices that are used to measure the output of an amplifier, so many kinds of equipment fall under this category. What we intend in this project is to create a simple circuit that can measure the output of any amplifier devices.


This is an easy trick to measure the output of an amplifier. Here resistor R2 acts as the load for the amp and it should be able to withstand twice the maximum power of the amp you are going to measure. The meter scale must be calibrated and with a little effort, you can get good results.

Audio Watt meter Circuit Diagram with Parts List

Audio Level Meter or Audio Power Meter
Audio Wattmeter Circuit Diagram


  • If 1A bridge is not available, make one with four 1N 4007  Diodes.
  • The resistor R2 must be twice the power of amp you are going to measure.
  • To calibrate the device, Connect the output of the amplifier to port 1. Also, connect an AC voltmeter to port1.
  • Set R1 fully off. That means full counter clockwise direction if wired conventionally.
  • Adjust the output of the amp to read 20Volt rms on the voltmeter. This is the equivalent of 50W on 8 Ohm load.
  • Adjust R1 for a full-scale deflection on meter M1. Now fix the wiper of preset R1 using some super glue.
  • Now reduce the voltage across the port 1 by reducing the output power of amplifier under test according to the table given below and mark the readings on the meter scale. The device is ready to measure.

Table for calibrating Meter


We have more Audio Circuits and Measurement Circuits that you may like to read; Take a look:

1. Audio Clipping Indicator Circuit

2. Audio Distortion Meter

3. Sound Level Meter

4. Audio Amplifier Circuit

5. Car Amplifier Circuit



  1. I am somewhere just beyond beginner’s experience and would like to build this circuit in a higher power environment than is described in the article, but I have a few questions that I was hoping someone could help answer for me.

    1a. It’s seeming like a resistor of 4 ohms with power handling of 500 watts or greater is hard to find, especially if I were going to build a meter to measure upwards of 1,000 watts, where the resistor would need to be able to handle more. Am I missing something or are they just not readily available? I’ve found some wirewound resistors in that range, but they are prohibitively expensive. Could it possibly be easier to arrange several resistors to achieve the same resulting impedance and power handling?

    1b. Can I not just build the speaker into the circuit instead of finding an equivalent resistor? This would have the benefit of the speaker being operational while getting power readings.

    2. Does changing R2’s resistance from 8 ohms to 4 ohms have any impact on the values of the other components? The best that I can tell is that it does not and only the calibration table would need to be changed.

    3. Is the panel meter an AC or DC meter? The diodes in the bridge are throwing me off here. Like high-power resistors, AC current panel meters don’t appear to be easy to find, either.

    Thanks in advance for any help that can be offered.

  2. seetharaman

    Hi Jay replace R2 as 8 ohms 500 watts resistance. Adjust R1 such that it measures 63volt RMS AC as full scale. The meter will; read 0 to 500 Watts RMS Power.

  3. What modification is required to measure 500W output power?