Amplifier Power and SPL Calculator
Calculate sound pressure level (SPL) at any distance from amplifier power and speaker sensitivity.
Convert between watts and dBW, find SPL with multiple speakers, and check hearing safety.
Speaker Sensitivity Speaker sensitivity is measured as dB SPL at 1 meter with 1 watt (1W/1m). Typical home speakers: 85–92 dB/W/m. PA speakers / line arrays: 95–105 dB/W/m. High-efficiency horn speakers: 103–110 dB/W/m. Higher sensitivity = louder with same amplifier power.
SPL from Power and Distance SPL at 1m = Sensitivity + 10 × log₁₀(Power in watts) SPL at distance d = SPL at 1m − 20 × log₁₀(d) The −20 dB/decade drop is the inverse square law for spherical radiation. A doubling of distance reduces SPL by ~6 dB; halving distance adds ~6 dB.
Doubling Power Every doubling of amplifier power adds +3 dB SPL. 10× power = +10 dB (sounds about twice as loud to human hearing). 100× power = +20 dB (sounds about 4× as loud). This is why going from 100W to 200W is barely noticeable (+3 dB).
Multiple Speakers (Coherent Addition) N identical speakers wired together (same polarity, in-phase): SPL increase = 10 × log₁₀(N) 2 speakers: +3 dB | 4 speakers: +6 dB | 8 speakers: +9 dB
Hearing Safety NIOSH recommended exposure limits: 85 dB = 8 hours | 88 dB = 4 hours | 91 dB = 2 hours | 94 dB = 1 hour 100 dB = 15 minutes | 110 dB = 1 minute | 120+ dB = immediate risk Reference: 0 dB SPL ≈ threshold of hearing; 194 dB = pressure of 1 atmosphere (theoretical max)