What is RMS voltage vs peak voltage?

RMS (Root Mean Square) voltage is the effective value used in power calculations. Peak voltage is √2 × RMS. Amplifier specs almost always quote RMS for continuous power ratings.

Why does impedance matter for power?

Power = V² / R, so halving the load impedance doubles the output power from the same voltage — provided the amplifier can supply the extra current without clipping or overheating.

What is speaker sensitivity?

Sensitivity is the SPL (in dB) produced by a speaker when driven with 1 watt at 1 meter distance. A typical home speaker is 85–90 dB/W/m; pro audio speakers often reach 95–105 dB/W/m.

How do I estimate SPL at different distances?

SPL drops 6 dB every time the distance doubles (inverse-square law). If SPL at 1 m is 100 dB, at 2 m it is ≈94 dB, at 4 m ≈88 dB.

dBW is power in decibels relative to 1 watt. dBW = 10 × log₁₀(P). 0 dBW = 1 W, 10 dBW = 10 W, 20 dBW = 100 W, 30 dBW = 1000 W.

What is voltage gain in dB?

Voltage gain (dB) = 20 × log₁₀(Vout / Vin). A gain of 20 dB means the output voltage is 10× the input voltage.

Amplifier Power Calculator

Name: Amplifier Power Calculator
Availability: InStock
Author: Nham Vu

Enter voltage, impedance, and gain to instantly calculate amplifier output power in watts and SPL in dB.

RMS Output Voltage (V)

Load Impedance (Ω)

Fill in the inputs and press Calculate to see results.

Formulas Used

P (W) = V² / R
dBW = 10 × log₁₀(P)
dBm = 10 × log₁₀(P × 1000)
I (A) = V / R
SPL = Sensitivity + 10 × log₁₀(P) − 20 × log₁₀(d)
Gain (dB) = 20 × log₁₀(Vout / Vin)

Summary

Enter voltage, impedance, and gain to instantly calculate amplifier output power in watts and SPL in dB.

How it works

Enter the RMS output voltage (V) your amplifier delivers into the load.
Enter the speaker or load impedance in ohms (typically 4, 6, or 8 Ω).
The tool applies P = V² / R to compute output power in watts and dBW.
Optionally enter speaker sensitivity (dB/W/m) to get estimated SPL at 1 m.
Use the Gain tab to calculate voltage gain (dB) from input and output voltages.

Use cases

Match amplifier output power to speaker continuous power rating.
Estimate loudness (SPL) before purchasing amp and speaker combinations.
Convert between watts and dBW for professional audio spec comparisons.
Check whether a home theater amp delivers enough headroom for a listening room.
Verify gain staging between preamp and power amp sections.
Calculate current draw (A) for amplifier circuit design.
Compare Class A/B/D amplifier specs using consistent units.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu