Amplifier Power
Find amplifier watts from output voltage into a speaker impedance.
About Amplifier Power
Rms power into a load is the output voltage squared divided by the impedance, while peak voltage is 1.414 times the rms value. Stated wattage only means something at a real impedance and distortion figure, so checking the math reveals an amp's honest output.
Formula
Amplifier Power
Power = voltage^2 / impedance
- THD
- Total harmonic distortion, the measuring condition for the rating
Worked example
With the default values below, Amplifier Power returns Power of 50.0. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Output voltageminimum 0.1 V
- 20 V
- Speaker impedanceone of 4 ohms, 6 ohms, 8 ohms, 16 ohms
- 8 ohms
- Measured atone of 1% THD, 0.1% THD
- 1% THD
Results
- Power
- 50.0 W
- Current
- 2.50 A
- Peak Voltage
- 28.3 V
Step by step
- 1Values used
- 2Amplifier Power
- 3Power= 50.0 W
- 4Current= 2.50 A
- 5Peak Voltage= 28.3 V
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Amplifier Power calculated?
Power = voltage^2 / impedance Rms power into a load is the output voltage squared divided by the impedance, while peak voltage is 1.414 times the rms value.
Why does Amplifier Power matter?
Stated wattage only means something at a real impedance and distortion figure, so checking the math reveals an amp's honest output.
What values do I need to enter?
This calculator takes 3 inputs: Output voltage, Speaker impedance, Measured at. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.