Speaker RMS to Watts Calculator
Determine actual continuous wattage and electrical current delivered into 2Ω, 4Ω, 8Ω, or 16Ω loudspeaker voice coils from measured RMS voltage.
Mode 1: RMS Voltage + Impedance
P = V² / RCalculate continuous electrical or speaker wattage using known RMS Voltage and load resistance/impedance.
Voltage × Load Impedance Power Matrix
Click standard test voltages and speaker impedances (2Ω, 4Ω, 8Ω, 16Ω) to immediately retrieve real continuous wattage.
Speaker Impedance & Power Delivery Physics
According to Ohm's Law and Joule's heating law, loudspeaker power dissipation is fundamentally governed by the relationship between alternating current voltage and voice coil load impedance:
Where V_RMS is the amplifier output voltage in Volts RMS, and R is the nominal voice coil impedance in Ohms (Ω).
Voltage, Impedance & Power Reference Matrix
| Output Voltage (V_RMS) | 2 Ω Load (Subwoofer) | 4 Ω Load (Car / PA) | 8 Ω Load (Home Hi-Fi) | 16 Ω Load (Horn / Pro) |
|---|---|---|---|---|
| 10.0 V RMS | 50.0 Watts (5.00 A) | 25.0 Watts (2.50 A) | 12.5 Watts (1.25 A) | 6.25 Watts (0.63 A) |
| 14.14 V RMS | 100.0 Watts (7.07 A) | 50.0 Watts (3.54 A) | 25.0 Watts (1.77 A) | 12.5 Watts (0.88 A) |
| 20.0 V RMS | 200.0 Watts (10.0 A) | 100.0 Watts (5.00 A) | 50.0 Watts (2.50 A) | 25.0 Watts (1.25 A) |
| 28.28 V RMS | 400.0 Watts (14.1 A) | 200.0 Watts (7.07 A) | 100.0 Watts (3.54 A) | 50.0 Watts (1.77 A) |
| 40.0 V RMS | 800.0 Watts (20.0 A) | 400.0 Watts (10.0 A) | 200.0 Watts (5.00 A) | 100.0 Watts (2.50 A) |
| 63.25 V RMS | 2,000.0 Watts (31.6 A) | 1,000.0 Watts (15.8 A) | 500.0 Watts (7.91 A) | 250.0 Watts (3.95 A) |
Understanding Power Compression in Loudspeakers
When an amplifier sends high continuous wattage to a speaker, the copper wire in the voice coil converts approximately 98% of that electrical energy into heat (since typical loudspeaker acoustic efficiency is only 1% to 2%).
Because copper has a positive temperature coefficient of resistance (+0.393% per °C), heating a voice coil from 20°C to 150°C increases its resistance from 8.0 Ω to approximately 12.1 Ω. This phenomenon—known as power compression—causes the speaker to draw less current, reducing acoustic output by 1.5 dB to 3.0 dB under heavy sustained loads.