Speaker Circuit Wattage Calculator

Calculate speaker/voice alarm circuit wattage loading and amplifier requirements per NFPA 72.

Input Parameters

Results

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Total Watt Load
W
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Amplifier Load
%
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Wire Power Loss
W
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Status
Note: Voice alarm systems per NFPA 72 Ch. 24 require 25V or 70.7V constant-voltage distribution. Keep amplifier loading below 80% and account for wire losses on long runs.

Reference

Total Load (W) = Number of Speakers x Tap Wattage Amplifier Load % = (Total Load / Amp Rating) x 100 Line Current I = Total Load / Line Voltage Wire Loss = I^2 x R_wire NFPA 72: 25V or 70.7V constant-voltage speaker circuits Keep amplifier loading under 80% for headroom.